The Hiawatha asteroid would have been nearly the size of the comet fragment that slammed into the Atlantic ocean in the 1998 film "Deep Impact." The comet in the film (Wolf-Biederman) was originally 7 miles wide but was broken apart by the nuclear space mission, a 1.5 mile wide fragment of the comet made it's way to Earth and hit the Atlantic ocean, resulting in the famous mega-tsunami scene.
Scientists perform research field work at the edge of the Greenland Ice Sheet while studying the age of the 19-mile-wide (31- km-wide) Hiawatha impact crater that is buried under ice six-tenths of a mile (1 km) thick in 2019.
In the 1998 film Deep Impact, the comet fragment impact generates a wave that is approximately 500 meters (about 1,500 to 1,800 feet) high when it reaches the East Coast and New York City. The initial wave height is roughly 600 feet at the point of impact in the Atlantic Ocean, growing to between 1,500 and 1,800 feet (or around 500 meters) as it slowed and piled up near the coast, towering over skyscrapers and completely submerging landmarks like the Statue of Liberty.
The largest confirmed asteroid to hit Earth is the Vredefort impactor, which struck South Africa about 2 billion years ago. The asteroid is estimated to have been between 20 to 25 kilometers (12 to 15.5 miles) in diameter based on recent studies (previous estimates placed it around 10 to 15 km). It was roughly twice the size of the asteroid that wiped out the dinosaurs (Chicxulub) and occurred long before complex multi-cellular life had evolved. It created the Vredefort Crater, the largest verified impact structure on Earth, with an original estimated diameter of 250 to 300 kilometers (155 to 190 miles), located near what is now Vredefort in the Free State, South Africa. This is the crater from space, you can see the black circular rings that represent the edge of the crater. The Vredefort asteroid impact released an energy equivalent to roughly 6.88 billion Hiroshima atomic bombs detonating simultaneously.
The Manicouagan crater in Québec is a lot older than Chicxulub: 214 million years. Known also as “the eye of Québec”, it became instantly recognizable as an impact crater after flooding of the Manicouagan river by Hydro Québec in the 1960’s. Now anyone can see it on Google Earth and many astronauts, including Canada’s own Chris Hadfield, have photographed it. Manicouagan is the fourth largest impact structure on earth. No tectonic forces have influenced or altered it since its inception. The asteroid hit nearly 1 billion year old Canadian shield rocks. After this event, not much else happened geologically, other than the normal amount of erosion, but it never was an area with high mountains so that wasn’t a whole lot. Then the ice caps of the Quaternary glaciations swept across it, nicely cleaning off debris and making it even more easily visible, so it’s a a rather pure and unchanged. The asteroid responsible for the Crater was approximately 5 kilometers (3 miles) wide.
1.85 billion years ago, a massive asteroid struck Sudbury, Ontario, melting part of Earth’s crust and creating the second-largest confirmed impact crater on Earth, behind only Vredefort in South Africa. 37 million years ago, another asteroid struck nearly the same place. The first impact was enormous. Scientists estimate the asteroid may have been 10–15 kilometers (6-9 miles wide), as big as the asteroid that wiped out the Dinosaurs (Chicxulub). The energy released was so great that vast volumes of rock were instantly melted, forming a huge pool of melted rock within the crater. This was not magma rising from deep inside the Earth. It was the surface rock itself, melted by the force of the collision into what geologists call an impact melt sheet. As that melt slowly cooled, heavy elements separated and concentrated within it, including nickel, copper, palladium, gold, and other platinum-group metals. Instead of remaining scattered through the crust, these materials became gathered and enriched by the cooling melt itself. Dense metal-rich sulfides settled downward, collecting along the base and edges of the structure. In effect, the impact briefly turned this part of Earth into a giant natural smelter, creating the mineral wealth that Sudbury is known for today. Much later, after nearly two billion years of erosion, deformation, and tectonic activity that reshaped the original crater, a second asteroid struck nearly the same place. That impact formed what is now Wanapitei Lake, a circular basin about 8 kilometers across. The younger crater is completely unrelated to the first event. It simply happened to land in terrain already shaped by one of the largest collisions in Earth’s history. Sudbury records two separate cosmic events that reshaped the same landscape, separated by a span of time almost impossible to comprehend.
Theia was a rocky, Mars-sized planetary body (about 5% to 10% of Earth's mass) that shared a similar orbit around the Sun. Theia collided with the early Earth approximately 4.4 billion years ago. The violent impact made the biggest asteroid strikes look like child's play. It blasted a mixture of molten rock and debris from both worlds into orbit, which quickly coalesced to form Earth's Moon. The energy released was approximately 143 trillion times greater than the Tsar Bomba (the most powerful nuclear bomb ever detonated. It released roughly 100 million times more energy than the asteroid impact that wiped out the non-avian dinosaurs. The immense heat and kinetic energy completely melted both bodies (or formed a massive vaporized/molten structure known as a synestia) and liquefied Earth's mantle and surface.
This book about the Chicxulub asteroid impact always sends chills up my spine every time I look at the cover, the blinding flash of light from the moment the asteroid hit. I mean, the impact produced a blinding, hyper-intense flash equivalent to 100 teratons of TNT (about 4.5 billion times the energy of the Hiroshima bomb or millions of nuclear weapons going off simultaneously). Across the daylight side of the planet, the impact generated an instantaneous, blinding mega-flash that outshone the Sun from regional distances and was visible globally. Even thousands of kilometers away, the sky lit up with extreme thermal radiation capable of causing flash burns, ignition of dry vegetation, and temporary or permanent blindness to any creature looking toward the horizon before the shockwave and ejecta rain arrived.
The Earth is about 7,926 miles (12,756 kilometers) wide at the equator. It is estimated by scientists that it would take an asteroid at least 6 to 10-miles-wide to collapse modern human civilization and an asteroid about 60 to 100-miles-wide to completely sterilize the Earth, boiling away the oceans, melting the crust, and destroying all life on our planet, even deep-subsurface extremophile life. It's just mind-bending to think about it. It's just mind-bending to think that the Earth is so big, and all it would take is a 60 to 100 mile-wide rock to end it all.
And just for clarification, no, a single spacecraft like NASA's DART could not deflect an asteroid as large as the Chicxulub impactor if such an asteroid were headed our way. The DART spacecraft weighed about 550 kilograms (1,210 lbs) and targeted Dimorphos, a small moonlet roughly 160 meters across. In contrast, the Chicxulub asteroid was roughly 10 kilometers (6 miles) in diameter and weighed about a trillion metric tons—roughly 200,000 to 250,000 times more massive than Dimorphos. A kinetic impactor like DART transfers momentum through physical crash force. Crashing a probe into a 10-kilometer-wide mountain of rock would barely register a change in its velocity unless executed millions of years in advance. It would be like a mosquito running into a bus. A massive object like the Chicxulub impactor requires early detection spanning many decades or centuries so a tiny change in speed can accumulate into a wide-enough miss distance by the time it reaches Earth's orbital path. Scientific studies indicate that kinetic impactors alone are inadequate for a 10 km scale threat. Deflecting or fragmenting an object of that magnitude would likely require multiple megaton-class nuclear explosive devices delivered via heavy-lift interplanetary spacecraft. Humanity currently lacks the immediate launch capability, pre-built interceptors, or global coordination needed to deploy a high-megaton nuclear deflection mission on short notice.
We are nowhere close to defending Earth from a cataclysmic asteroid
You can't throw a DART at everything in space.
By: Tom Hartsfield
February 17, 2023
An enhanced photograph of ejected plumes caused by DART’s impact on Dimorphos. (Credit: ASI / NASA / APL)
Last September, NASA smashed a spacecraft into a small asteroid. The results were impressive, as shown in the image above.
The Double Asteroid Redirection Test, or DART, was a success as a prototype technological demonstration. But what can we say about the impact of the mission? What does it mean for our chances of defending the planet from cosmic calamity? Unfortunately, not much — not yet, anyway.
NASA’s DART was a successful mission
The spacecraft performed well. A camera aboard DART captured the scene as the craft passed by Didymos, a near-Earth asteroid. DART’s target was Didymos’ satellite, Dimorphos. The target asteroid expanded to fill the frame, and the test ended abruptly with a head-on strike.
Had the craft hit at a wide angle to the geometric center of the rock, the results could have been different. The asteroid might have rotated or wobbled without slowing its translational motion. (Think of how striking the edge of a billiard ball imparts what competitors call English, while striking the center directs the ball purely forward.) Telescopes detected giant plumes of ejected material thrown out into space, another good sign. Mass sprayed off in one direction imparts force in the other direction on the sprayer.
A few days later, NASA announced that the small asteroid’s orbit around the larger one was altered by an amount large enough to clearly measure. The orbital period dropped by about 32 minutes, from 11 hours and 55 minutes to 11 hours and roughly 23 minutes. This was at the high end of estimates going in, so it is good news.
However, that measurement alone does not tell us how well the tactic would work on an asteroid that poses a real threat — which is what we really want to know. Eventually, NASA will have more complete data, allowing researchers to examine details more carefully. For now, our answers are partial. But we can make further estimates and touch on the science behind asteroid deflection.
Interstellar gnats
A planetary defense mission works by altering the motion of an asteroid by a tiny, tiny amount. Let’s say you rolled two bowling balls down one regulation bowling lane. A gnat flies up the lane and smacks into one of the balls. The impact slows that ball by a miniscule amount, too small to reasonably measure. At the end of the lane, the balls will strike at the exact same time, to the human eye. But if the lane is 1,000 miles long, the gnat-slowed ball will arrive slightly tardy at the far end.
The lanes of space are billions of miles long, so you don’t have to hit the ball very hard if you hit it very far in advance.
Let’s say that by smashing a spacecraft into it, we reduce an asteroid’s velocity by 1/10,000 of 1 percent. The distance it travels in a day might now be reduced from, say, 864,000,000 meters to 863,999,136 meters. So, the asteroid’s expected position slows by 864 meters (0.864 km) each day after the impact. Given that Earth is over 12,000 km in diameter (nearly 8,000 miles), it takes several thousand days for the slow-down to accumulate to its intended effect: namely, allowing Earth to slip past the asteroid.
NASA hoped to slow Dimorphos by about one mile per day. In theory, this would be enough to shift an Earth impact to a near-miss, if the asteroid could be struck ten years plus a few weeks in advance of an impending collision.
What we do not know yet is whether DART’s impact slowed the asteroid more than NASA hoped. We can make some estimates by using the minimal eccentricity of Dimorphos’ orbit about Didymos — which is nearly zero, or circular — the decrease in its orbital period after impact, and NASA’s predictions. In the best-case likely scenario, the impact slowed Dimorphos by about 4 miles per day. In the worst-case likely scenario, it might have slowed it by only one mile per day. The middle-of-the-road estimate is somewhere around 2.5 miles per day. Values outside this are of course possible, and we don’t know enough yet to be sure. These numbers are in line with what NASA hoped for going in, although they are on the high end of expectations.
Re-running our simple calculations, in our best-case outcome, striking Dimorphos 2.5 years in advance would give just enough time to shift an impact trajectory to one that scraped the atmosphere but missed. In the worst case, we would need to impact it ten years ahead of time. How much protection does that afford us?
A nice start, but a long way to go
The Tunguska event was likely caused by a rock about 200 feet across. We can roughly estimate that it had less than 1/20 the mass of Dimorphos. The famous Barringer Crater in the Arizona desert, nearly 600 feet deep, was caused by a similarly sized rock of different composition. Either of these could have destroyed a city unlucky enough to sit at the impact point. Rocks of this size could be effectively deflected by DART less than a year before a predicted strike. The catch is that detecting them is very difficult. Ongoing efforts continue to discover new near-earth asteroids on a nearly daily basis. Objects like the Chelyabinsk meteor in 2013 are often detected only when the fireball lights up the sky.
Dimorphos was discovered in 2003. If it had been on a collision course for, say, 2030, we could probably prevent an impact. Didymos, about which it orbits, was discovered in 1996.
This is where the bad news starts.
Let’s say that Didymos was due to hit Earth. Its diameter is about 4.5 times that of Dimorphos. That means Didymos has something like 95 times more mass. In this case, DART would have to impact it somewhere between 190 and 950 years in advance to alter its course sufficiently. We only discovered it 26 years ago. If we needed to deflect it within a few years, we would have to hit it 100 times harder than DART hit Dimorphos. That means mass and velocity, multiplied together, must be on a scale 100 times greater than that of DART. This is possible, but it would stretch our current capabilities. We could add mass through a series of large launches, perhaps using Falcon Heavy launch vehicles. Additional engines could be launched to boost velocity. As for rocks larger than Didymos, they would pose a much greater problem.
The famous Chicxulub impactor that caused a mass extinction 66 million years ago was roughly 10,000 meters in diameter. The mass of this object — about 200,000-fold greater than Didymos — was significant enough that a spacecraft like DART would have to impact it millions of years in advance to avoid an extinction-level impact. No conceivable improved version of DART is capable of preventing such an event. For that, we would need far more powerful countermeasures. An investigation of this problem was carried out by scientists T.J. Ahrens and A.W. Harris, who analyzed the necessary countermeasures against asteroids of varying sizes. For small rocks, they conclude that a mission like DART, perhaps scaled up a bit, could be enough — as DART indeed just showed.
For rocks bigger than Didymos, but much smaller than Chicxulub, the impactor would need thousands of times more momentum. We cannot easily make a craft thousands of times faster or thousands of times more massive than DART with current rocketry technology. Nuclear weapons could impart enough push to do the job, with certain careful considerations about the composition of the asteroid, the location of the blast, how well the blast could be directed, the amount of ejecta blasted away, and so forth.
For giant objects like Chicxulub, the only presently feasible option is a truly enormous nuclear blast. A device of many megatons might give us a chance. Fortunately, we are likely to spot asteroids of this size far in advance.
DART was a useful first step toward asteroid deflection capability. However, Dimorphos is very small. We have a long way to go before we can defend against truly catastrophic collisions.
And also just to clarify, no, a standard Chicxulub-sized asteroid cannot "sneak up" on Earth. Because an object of that scale (10 to 15 kilometers wide) is incredibly massive and reflects a significant amount of light, automated planetary defense telescope systems have already mapped and tracked virtually 100% of all Near-Earth Asteroids (NEAs) of this size. Astronomers can calculate their orbits centuries into the future, and none are currently on a collision course with Earth. However, there are two extreme, highly unlikely astronomical scenarios where a planet-killer could catch us with limited warning:
The Solar Blind Spot
The most significant limitation of Earth's current ground-based optical telescopes is the glare of the Sun. If a previously unknown, highly eccentric asteroid approached Earth directly out of the Sun's direction, it could remain hidden in the daylight sky until it was very close. Even so, because a 10 km object is so large, we would still likely spot it weeks or months in advance as it crossed the inner solar system, rather than discovering it only hours before impact.
Long-Period Comets or Interstellar Objects
The real "wild card" is not a local asteroid, but an object originating from the outermost edges of our solar system (the Oort Cloud) or from another star system entirely.
• Long-Period Comets: These giant chunks of ice and rock spend thousands of years in deep space where they are completely dark and invisible to us. If one shifted into an Earth-crossing orbit, it would travel at extreme speeds.
• Warning Time: We would only detect it once it grew close enough to the Sun to start heating up and forming a visible tail. For an object that massive, we might only get a few months to a couple of years of warning before impact—which, as established, is not enough time for humanity to mount a successful deflection mission.
In summary, the odds of an asteroid the size of the Chixculub impactor sneaking up on us are effectively zero. The odds of a giant, undetected comet appearing out of the deep outer solar system on a direct collision course are mathematically real, but extraordinarily rare, happening only once every tens or hundreds of millions of years.
The History Channel did a 10-part series called "Doomsday: 10 Ways the World Will End", most of it is available on YouTube for viewing. It interviews some of the world's best physicists, paleontologists, and experts and discusses the many threats to our existence, asteroids, Black holes, Gamma Ray bursts, Supervolcanoes, Nuclear War, rogue planets, and even our own sun. Being interested in space, science, physics, and almost everything about life in general, you can't help but wonder how it will all come to an end.
Gamma-ray bursts are quite insane to think about. A gamma-ray burst (GRB) cannot physically blow up or destroy the planet Earth, but a close enough hit could wipe out most life on the surface. A GRB is a hyper-energetic cosmic explosion from a collapsing massive star or merging neutron stars. It releases more energy in a few seconds than our Sun will produce in its entire lifetime. The energy shoots out in narrow, intense beams from the poles of the exploding or merging object. If a beam directly targeted Earth from within a few thousand light-years, the high-energy photons would tear apart nitrogen and oxygen molecules in the upper atmosphere. This destroys the ozone layer. With the ozone layer gone, intense ultraviolet (UV) radiation from the Sun would flood the surface. The ozone layer acts as a global shield by absorbing dangerous solar ultraviolet (UV-B and UV-C) rays. If a nearby gamma-ray burst (GRB) stripped away or severely thinned this layer, that barrier would vanish and our skin would be left completely exposed to the hellish wrath of the sun's radiation. This could also trigger massive ecological collapse, plant and marine die-offs, and a mass extinction event. Some scientists suggest a GRB may have contributed to a past extinction, such as the Ordovician mass extinction 450 million years ago. To cause a mass extinction, the GRB would need to occur relatively close within our own galaxy—typically estimated within a few hundred to a few thousand light-years. According to the European Space Agency, there are no known candidate stars capable of producing a GRB close enough to threaten Earth (with safe zones generally falling within 200 to several thousand light-years). Distant bursts are harmless. Billions of light-years away, GRBs like the record-setting "BOAT" burst observed by NASA/ESA only slightly ionize Earth's upper ionosphere without posing any danger to life on the ground.
You know, it's fascinating. The famous and legendary astrophysicist Neil degrasse Tyson once said that if he could choose a way to die, he would like die by falling into a black hole. He stated he would choose falling into a black hole as his preferred way to die because it serves as the ultimate cosmic experiment, allowing him to experience intense relativistic physics and transmit data back to scientists before being destroyed. He views it as a rare opportunity to gather data from an extreme gravitational environment that cannot be replicated in a terrestrial laboratory. He has described the process of falling feet-first, where the gravitational pull on your feet is much stronger than on your head, stretching and compressing the body into a stream of particles—a phenomenon known as spaghettification. He noted that, in theory, an observer equipped with specialized transmitters could relay information back to scientists outside the event horizon before crossing the point of no return. Due to extreme gravitational time dilation, time passes differently near a black hole compared to the rest of the universe, offering a surreal window into cosmic mechanics. Black holes are extremely mysterious and complex.... and quite terrifying. Contrary to popular myth, black holes do not suck things in like a cosmic vacuum cleaner, black holes pull objects using normal gravity, not a mysterious suction force. A black hole exerts the exact same gravitational pull as any other star or object of the same mass. If the Sun were suddenly replaced by a black hole with the exact same mass, the Earth would not get sucked in; it would continue orbiting safely in the same path. Danger only begins when an object gets too close and crosses an invisible boundary called the "event horizon", two of the scariest words in science. This is the "point of no return" where the gravitational pull becomes so strong that nothing—not even light—can escape. Objects do not automatically fall in. Planets, gas, and stars can safely orbit black holes if they keep enough distance or have enough sideways speed. If something gets too close to the event horizon, extreme gravitational differences between the front and back of the object stretch it out like a strand of spaghetti, the spaghettification process. A black hole is a region in space where a massive amount of matter is packed into a tiny space, creating a gravitational pull so strong that nothing—not even light—can escape its bounds. The "event horizon" is the invisible boundary surrounding a black hole, it is the point of no return, once anything crosses it, it cannot break free from the gravity. The "singularity" is the center of a black hole where matter is crushed down to a point of infinite density and zero volume, where the laws of physics completely break down. The "accretion disk" is a swirling ring of superheated gas, dust, and debris that often orbits around a black hole, glowing brightly in X-rays and other light wavelengths. There are four main types of black holes.
• Stellar-mass Black Holes (up to a few dozen solar masses): Formed when a giant star runs out of fuel and collapses under its own weight in a supernova.
• Supermassive Black Holes (millions to billions of solar masses): Massive giants located at the centers of nearly all large galaxies, including Sagittarius A* at the heart of the Milky Way.
• Intermediate-mass Black Holes (hundreds to thousands of solar masses): A rarer, mid-sized category whose exact formation remains under scientific study.
• Primordial Black Holes (theoretical): Tiny, hypothetical mini black holes proposed to have formed during the first moments after the Big Bang.
The strength of gravity inside a black hole is infinite at its absolute center (the singularity), but its pull depends entirely on how close you are to it. From a distance, a black hole has the exact same gravitational pull as any normal object of the same mass. If our Sun were replaced by a black hole with the exact same mass, Earth would not get sucked in—it would continue to orbit normally (though it would be very cold). The extreme, inescapable gravity only happens when you get too close. Gravity depends on mass and distance. Because a black hole packs massive amounts of matter into a tiny, compressed point, you can get incredibly close to its entire mass. As you approach a black hole, you reach the "event horizon." At this precise boundary, the gravity becomes so strong that the escape velocity (the speed required to break free) exceeds the speed of light. Since nothing can travel faster than light, absolutely nothing—not even light itself—can escape once it crosses this line. If you were to fall into a black hole feet-first, the gravity pulling on your feet would be vastly stronger than the gravity pulling on your head. This extreme difference in gravitational force over a short distance is called a tidal force. It would stretch an object out horizontally and pull it vertically, a real scientific phenomenon colorfully known as spaghettification. Yes, if Earth got too close to a black hole, spaghettification would absolutely occur. The planet would be stretched, torn apart, and eventually swallowed as a stream of debris. However, how and when this happens depends entirely on the size of the black hole.
Scenario 1: A Stellar-Mass Black Hole (The Violent Stretch)
If Earth approached a smaller black hole (about 5 to 30 times the mass of our Sun), the tidal forces would strike long before the planet even reached the event horizon. The gravity on the side of Earth closest to the black hole would be thousands of times stronger than the gravity on the far side. This massive difference in pull would overcome the internal gravity holding Earth together. The result, Earth would be violently ripped into a long, thin stream of rock, magma, and gas, resembling a cosmic noodle before crossing the threshold.
Scenario 2: A Supermassive Black Hole (The Hidden Trap)
If Earth approached a supermassive black hole (like the ones at the center of galaxies, millions of times the mass of our Sun), a strange quirk of physics occurs. Because the black hole is so enormous, its event horizon is massive, and the tidal forces at the edge are surprisingly gentle. Earth could actually cross over the event horizon intact without being spaghettified yet. Once inside, however, Earth would be completely trapped in the region of inescapable gravity. As Earth continued its plunge toward the central singularity, the gravity would intensify exponentially. Spaghettification would still happen, but it would take place inside the black hole, hidden from the rest of the universe.
What We Would Experience First
Long before the physical rock of Earth stretched into a noodle, the atmosphere and oceans would be stripped away. Extreme earthquakes, super-volcanoes, and catastrophic tidal waves would tear across the surface as the black hole's gravity began to warp the planet's shape.
Theoretically speaking, yes, a black hole could enter our solar system and end the world. While space is mostly empty and the chances are incredibly small, there is no law of physics that prevents a wandering black hole from passing through our cosmic neighborhood. A black hole wouldn't even need to swallow Earth directly to destroy life as we know it. Depending on its size and path, its entry into our solar system could end the world in a few different ways.
Scenario 1: A Wandering Stellar Black Hole (Gravitational Chaos)
Most black holes are "stellar-mass" black holes, created from collapsed stars. They can drift through the galaxy undetected because they don't emit light unless they are actively feeding.
If one passed through our solar system, its massive gravitational pull would act like a cosmic bowling ball scattering pins:
• Orbits Destabilized: It would alter the orbits of the planets. Earth could be pulled closer to the Sun, scorching the surface, or flung further away into freezing deep space.
• Flung Out of the Solar System: Earth could be entirely ejected from the solar system, turning us into a frozen, dark "rogue planet" where life could not survive.
• Asteroid Showers: The black hole would disturb the Oort Cloud and Kuiper Belt (the icy regions at the edge of our solar system), sending millions of massive comets and asteroids hurtling directly toward the inner planets.
Scenario 2: A Rogue Supermassive Black Hole (Instant Obliteration)
Supermassive black holes stay at the centers of galaxies. However, when galaxies collide, these monsters can occasionally be kicked out into deep space.
• If a supermassive black hole entered our solar system, its gravity is so overwhelming that it wouldn't just disrupt orbits—it would swallow the Sun and all the planets whole.
• The solar system would simply cease to exist in a matter of days or weeks.
Scenario 3: A Micro "Primordial" Black Hole (The Silent Bullet)
Scientists have theorized that tiny black holes, the size of an atom but with the mass of a mountain, could have formed during the Big Bang.
• If a micro black hole passed through Earth, it would act like an unstoppable, hyper-dense bullet.
• It would shoot right through the planet from one side to the other in minutes.
• While it might not swallow the Earth, the energy released by its passage could trigger catastrophic, global earthquakes and volcanic eruptions.
The Real-World Reality Check
While this is a terrifying theoretical concept, astronomers actively track the movements of nearby stars and cosmic structures. There are currently no known black holes anywhere near our solar system, and space is so vast that the probability of one colliding with us is practically zero in our lifetime. This is a fascinating interview with astronomer Phil Plait about a black hole apocalypse.
Could the Earth Be Destroyed by a Black Hole?
If a black hole came wandering through the solar system, would we notice? We're joined by the Bad Astronomer, Dr. Phil Plait, to chat about the possibility of Earth meeting its end via gravitational catastrophe.
Transcript
ERIC: From the Museum of Science in Boston, this is Pulsar, a podcast where we search for answers to the coolest questions we've ever gotten from our visitors. I'm your host, Eric. And today we're going to put our planet in peril by answering a question we get with surprising frequency. Could the earth ever be destroyed by a black hole? Joining me is the person I usually think of when I'm contemplating planetary annihilation: the Bad Astronomer, Dr. Phil Plait, author of Death From the Skies: These Are the Ways the World Will End. Dr. Plait, thanks so much for being here on Pulsar.
PHIL: Oh my pleasure, I'm really happy to support the museum.
ERIC: So it turns out a lot of people ask us this question only having heard of black holes as awesome, powerful things in space, and not really knowing what they are. So can we start with an overview of what makes a black hole a black hole?
PHIL: Sure! What makes a black hole a black hole is its intense gravity. The gravity that you feel from an object depends on two things: how much stuff is in that object - how much mass it has, and how close you are to it. And if you take a lot of mass and squeeze it into a smaller and smaller volume, you can get closer and closer to it, because it's smaller. And when that happens, the gravity gets stronger and stronger. And at some point, if you have enough mass squeezed into a tiny enough volume, you get a black hole. Black holes have really, really, really strong gravity.
ERIC: Yeah that Hollywood, maybe like, general perception of a black hole being a hole that opens in space: not really true, it's just really powerful gravity. It still can do a lot of annihilation, but it's not something that's going to just appear somewhere, like, right next to the earth.
PHIL: And the power of the black hole comes from the fact that its gravity gets more intense the closer you are to it. And if you're heading towards the sun, there's only so close you can get to the sun before you kind of smack into its surface. And that's the most gravity you can feel. But if you take the sun and then compress it down into a ball that's just a few miles across. Yeah, it becomes a black hole, you can keep getting closer and closer to it, instead of being basically 400,000 miles from the center or something like that, you can get much, much, much closer, you can just be a few miles from the black hole. And so the gravity you feel is really, really strong. And that's where their destructive power comes from.
ERIC: Now we get that question a lot, too. What would happen if the sun magically turned into a black hole?
PHIL: Now gravity fades with distance. Replace the sun with a black hole, we wouldn't even really notice. I mean, we'd freeze, right? We wouldn't be getting light and heat. But the gravity we'd feel from the Sun is the same because the mass of the Sun stays the same. And we're the same distance from it. That's the critical thing. So if you take a black hole and put it really far away, you don't feel that much from it.
ERIC: Okay, so distance is a factor. But if one got closer, could a black hole destroy the Earth?
PHIL: And I want to be careful here, because I get this question a lot, too. And let me say, can a black hole destroy the Earth? Yes. Will a black hole destroy the Earth? Probably not. You know, you never say no. Because you have to kind of qualify it and say, look, there are a lot of black holes in the Milky Way galaxy, millions and millions of them really, and that sounds terrifying. But space is big. And that's why we call it space. And they're really, really, really far away. And if you do the math, it's actually fairly complicated. How often would a black hole get close enough to the sun into the earth to do damage? And the answer is essentially never, over the entire age of the universe. This probably has not happened. If it had happened, we wouldn't be here. So you know, right away that tells you over 4 billion years it hasn't happened, even once.
ERIC: So nothing to lose sleep over, which is great. But say one did wander into the solar system. What kind of things would we notice first?
PHIL: So if we pretend that this will happen, and again, probably not, but if it were to happen, your typical black hole, which is 10 or 20 times the mass of the Sun, is very small. It's only a few dozen miles across, and it's black, so it doesn't emit light. And if it's just out there in space, we won't see it. Now it may have some effect on starlight. Starlight passes it, it gets bent and warped. And we might notice that, that would be that would be pretty cool, although terrifying. But the effect it would have gravitationally on us would first probably be with the outer planets or even these chunks of ice and rock that orbit the Sun even out past Neptune. These are like gigantic comets and the gravity of the black hole would probably disturb those. And we see these things falling in towards the sun and think, Wow, we're getting a lot of comets lately, what's going on with that? Oh, maybe it's a black hole. And then as it gets closer, the orbits of the planets would change. And we'd see that because we know how the planets go around the sun. And then if it got close enough to Earth, then it would be bad. The moon might get pulled out of its orbit. And then there are the tides. Gravity changes with distance. The closer you are to something, the stronger the gravity. And if one side of the Earth is closer to the black hole than the other side, that means that there's a different force on the two sides of the earth. And that will stretch us like an egg. And if the black hole gets close enough, it will tear the earth apart.
ERIC: Sounds like all kinds of bad things could happen if a black hole were to wander by, but as you said, space is really big. What is the closest one that we know of to the earth?
PHIL: That's a hard question to answer. In fact, for a long time, it was this one called Cygnus X one that's over 1,000 light years away. There is one recently discovered, which I'm going to put in air quotes, which is closer, but it's not convincing that it's a black hole just yet. The problem is because they're black, we can't see them directly. But if they're orbiting a star, we can see their effects on the star. And it's not clear that what we're seeing going on with the star is actually because of a black hole.
ERIC: But still not really in our neighborhood. 1,000 light years away, that's really far. And that's not gonna affect us anytime soon, or ever.
PHIL: That's correct. For something to have an actual effect on us, it would have to be certainly no farther than a light year away. If we're talking about sort of a normal black hole that we we talk about when a star explodes and the core collapses, and it forms what we call a stellar mass black hole, it would have to be pretty close. And the odds of that happening are extremely rare. Think of it this way: there are hundreds of billions of stars in the galaxy, thousands of times more stars than there are black holes. And yet a star has never really passed close enough to the Earth to damage us over the four and a half billion years we've been around. So the odds of a black hole getting closer are a thousand times worse. So I'm not too concerned about it.
ERIC: Now, black holes don't show up too often in science fiction, but you got your nickname by pointing out the bad astronomy in movies, like nonsense with moon phases not changing, or magical orbits on space stations that have unexplained gravity. So I have to ask, are there any particularly bad or good representations of black holes from popular films?
PHIL: Yeah, if you watch Disney's The Black Hole from the 1970s, it's not great. But the movie Interstellar, which came out a few years ago, and I'll preface this with saying, I didn't care for it, not my cup of tea, but the representation of black holes, it was done very well. They talk about the intense gravity, they talk about how black holes can spin, they talk about the tides from a black hole. And they also talked about, and this was an important part of the movie, time dilation. The closer you get to a black hole, and the stronger the gravity is, your clock ticks slower. Time flows more slowly for you compared to somebody really far away from the black hole. And that's a real effect. It's not like a mechanical thing where your watch is just slowing down. Time literally moves more slowly. Not only was that depicted fairly well in the movie, it was a plot point. And it was kind of kind of an important thing that happened there. So that was pretty neat. And also just the visual representation of the black hole. The way light bends around it. That was all done really really well.
ERIC: Alright, so it sounds like we shouldn't lose any sleep over black holes. But that doesn't mean we shouldn't keep studying them because they they do sound pretty awesome. And they do sound like some of those powerful forces in the universe.
PHIL: That's correct.
ERIC: All right, Dr. Plait. Thanks so much for joining us here on Pulsar.
PHIL: Thank you.
ERIC: For more awesome and terrifying things that could destroy entire planets, come talk to our staff at the Charles Hayden Planetarium at the Museum of Science. And be sure to check out Death From the Skies: These Are the Ways the World Will End. wherever science-y books are sold. Until next time, keep asking questions.
One of the greatest scenes in film history, Interstellar, Joseph Cooper enters the supermassive black hole named Gargantua. Gargantua is a massive, rapidly spinning black hole that dominates the planetary system visited by the crew. After performing a gravitational slingshot maneuver with the spacecraft, Cooper detaches from the main ship and falls past the event horizon into Gargantua. Inside, he enters a physical manifestation of five-dimensional space known as the Tesseract, allowing him to send quantum data back to Earth via his daughter Murphy Cooper. I just about fell off of my sofa the first time I watched this scene.
It's fascinating, scientists have directly imaged two individual supermassive black holes using the Event Horizon Telescope, alongside the first radio image of a binary black hole system. The observations for the first direct black hole images were taken in April 2017 by the Event Horizon Telescope network:
• Messier 87 (M87)* (the supermassive black hole in the M87 galaxy): The data was captured in April 2017 and the historic first image was publicly released on April 10, 2019.
• Sagittarius A* (the supermassive black hole at the center of the Milky Way): The data was also captured in April 2017 (though processing took longer due to data shipment from the South Pole), and the image was publicly released on May 12, 2022.
Folks, I don't think people understand just how big black holes can get. It's mind bending. The largest known and reliably measured black hole in the universe is TON 618, though Phoenix A is theorized to be larger. TON 618 is estimated at 66 billion times the mass of our Sun (some lower recent estimates place it around 40.7 billion solar masses). It is a hyperluminous, radio-loud quasar. Its event horizon is so large that it spans roughly 390 billion kilometers, meaning entire solar systems could fit inside it comfortably. It sits approximately 18.2 billion light-years away from Earth.
This is what a black hole looks like in space without it's accretion disk, very eerie. Black holes only have accretion disks if they are accreting, actively feeding on gas and dust. Scientists find black holes indirectly by observing how their immense gravity and physical processes affect nearby matter, light, and spacetime. Because black holes do not emit or reflect light, astronomers use several key methods to detect them:
• Stellar Orbital Dynamics: Astronomers watch stars orbiting an invisible, super-dense point in space. By tracking their speed and paths, scientists calculate the hidden mass using gravity laws. This method confirmed Sagittarius A* at the center of the Milky Way.
• Accretion Disk X-rays: When a black hole pulls gas and dust from a companion star, the matter forms a spinning disk called an accretion disk. Friction heats the gas to millions of degrees, causing it to glow and emit high-energy X-rays that space telescopes can capture.
• Gravitational Waves: When two black holes spiral together and merge, they send violent ripples through the fabric of space-time. Instruments pick up these waves to measure the masses of the colliding bodies.
• Gravitational Lensing: A black hole's strong gravity bends and magnifies light coming from a star or galaxy directly behind it. This distortion reveals isolated or wandering black holes that would otherwise stay hidden.
• Direct Shadow Imaging: Global networks of radio telescopes, such as the Event Horizon Telescope (EHT), link together to capture the dark shadow of a black hole silhouetted against its glowing ring of superheated plasma (such as in M87 and the Milky Way center).
You see this image on Facebook a lot, an AI generated image of what it would look like from Earth if a black hole were approaching. This is complete fiction. While the design of the black hole itself is highly accurate—modeled after the iconic "Gargantua" from the sci-fi movie Interstellar—the depiction of it looking like this in Earth's sky is scientifically impossible. If a black hole large enough to be resolved by the naked eye were actually this close to Earth, the reality would look vastly different. The Atmosphere and Earth would already be destroyed. Before a black hole could ever get this visually large in the sky, its immense gravitational and tidal forces would completely pull apart the Earth. Long before it reached this point, the atmosphere would be stripped away, and the planet would experience catastrophic earthquakes, global volcanism, and spaghettification. There would be no houses or telephone poles left standing to view it from. A real black hole doesn't just sit perfectly on top of a sunset sky. Because its gravity is so intense, it acts as a massive lens. It would warp, stretch, and duplicate all light passing behind it, completely distorting the horizon, the stars, and the sky surrounding it into chaotic rings and arcs of light. The glowing orange ring you see is the accretion disk, made up of superheated gas and dust spinning at near light-speed. The extreme X-rays and gamma radiation radiating from this disk would completely strip away Earth's ozone layer and atmosphere, vaporizing life on the surface and sterilizing the planet. The accretion disk of a black hole typically reaches temperatures from 1 million to over 100 million Kelvin (roughly 1.8 million to 180 million degrees Fahrenheit), with inner hot regions and surrounding coronae climbing even higher.
Love this up close image of a black hole. This is a remarkably realistic depiction of a black hole, though it includes a few specific compromises made for cinema. This image shows Gargantua, the fictional supermassive black hole created for Christopher Nolan’s 2014 film Interstellar. Rather than hiring artists to guess what it would look like, the visual effects team collaborated with Nobel Prize-winning theoretical physicist Kip Thorne. They fed actual mathematical equations from Einstein’s Theory of General Relativity into custom rendering software. The simulation was so precise that the team actually published peer-reviewed astrophysics papers about what they discovered during rendering.
Stunning visual of the black hole Gargantua from the film Interstellar. The glowing accretion disk and warped light around the black hole. Gravitational lensing bends the light of the disk both above and below the black hole's shadow, creating the bright, halo-like ring appearance.
The giant waves on Miller’s planet in the film Interstellar were caused by the extreme gravitational tidal forces of the supermassive black hole, Gargantua. Because the planet orbited dangerously close to Gargantua, the black hole's gravity pulled intensely on the planet's oceans. Instead of normal rolling ocean waves, the water was deformed into massive, permanent tidal bulges (up to 4,000 feet or roughly 1,200 meters high). Rather than rotating smoothly, the planet experienced a wobble or back-and-forth balance as it orbited. This motion caused the giant bulges to "slosh" across the shallow ocean roughly once every hour. Because most of the planet's water was tied up in these towering bulges, the rest of the ocean stayed very shallow (only knee-deep where the crew landed), making the passing wave look like a towering, moving wall. Another phenomenal scene.
A binary black hole is an astronomical system made of two black holes that orbit closely around a shared center of gravity. These systems are generally divided into two main categories:
• Stellar-mass binary black holes: Formed from the remnants of massive binary star systems that separately collapse into black holes, or created through dynamic encounters and mutual capture in dense star clusters.
• Supermassive binary black holes: Involve giant black holes with millions or billions of solar masses, believed to form when two galaxies merge.
As the two black holes spiral closer and closer together, they distort space-time and release immense amounts of energy in the form of gravitational waves—ripples in the fabric of the universe predicted by Albert Einstein. Eventually, the two black holes collide, essentially eating each other, and merge into a single, larger black hole. Scientists first directly detected a binary black hole merger in 2015 using observatories like LIGO, opening a new era of gravitational-wave astronomy. This is a great article about their behavior.
Bad Astronomy
Merging black holes blast out light… but not for the reason you'd think
By: Phil Plait
Jun 26, 2020
A binary pair of black holes about to merge together, near the huge disk of material swirling around a supermassive black hole in a distant active galaxy. Credit: Caltech/R. Hurt (IPAC)
When two black holes eat each other, they release a lot of energy.
A lot. A significant fraction of the mass of the black holes is converted into energy, radiating away as gravitational waves, ripples in the fabric of spacetime. These can have as much energy as — and I am not kidding you here — tens of thousands of times as much as the Sun will radiate over its entire lifetime… and they blast away in a few seconds. Put another way, during that time the black holes emit hundreds of millions of times more energy than all the stars in the galaxy combined.
That kind of power is terrifying. Mind crushing. Yet, for all that, the event itself is entirely invisible, giving off no light at all. It's possible under some specific circumstances some light will be emitted, but generally speaking the two black holes merge, scream out their gravitational waves, and become a single, somewhat larger black hole… and all this without a photon emitted.
So no light is produced directly. But indirectly, it turns out things can be different.
Artwork depicting two black holes orbiting each other, shortly before they merge and blast out gravitational waves. Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)
On 21 May, 2019, the LIGO and Virgo gravitational wave observatories detected a pair of black holes merging somewhere in the Universe — the event was given the designation S190521g. Triangulating the signal, it was found to come from a spot in the sky the direction of the constellation Coma Berenices. Within moments, an automated alert was sent out to telescopes all across the planet to look for some sort of optical signal.
No flash of light was seen. At least, not right away.
On Mt. Palomar in California there is a 1.2-meter telescope with a 600 megapixel camera that can see a whopping 47 square degrees of sky at a time, a huge field of view. Called the Zwicky Transient Facility it scans the sky looking for things that go flash (or just change brightness) in the night.
34 days after the LIGO-Virgo gravitational wave detection, it was looking toward Coma Berenices and saw a flare, a brightening, coming from the distant galaxy AGN J124942.3 +344929 (let's call it J1249 for short). This is an active galaxy, one with a supermassive black hole in its heart (with a mass of 100 million times the Sun, so decently huge) that's actively eating material. As it falls in, this material gets very hot and emits quite a bit of light, making this galaxy visible even from its forbidding distance of 4.6 billion light years.
The flare detected lasted for about 50 days. Over that time, the amount of energy it emitted was huge, about 1044 Joules — more energy than the Sun will emit over its entire lifetime!
A month after a pair of black holes merged, a huge flare of light was released from the galaxy AGN J124942.3 +344929 (arrowed), possibly as the merged black hole interacted with material around a third supermassive black hole. Credit: Aladin / DSS
Active galaxies are known to flare, but this particular one had been quiet, or at least had a steady luminosity, for a year around the flare. Looking at the galaxy's history (and the histories of other galaxies) and applying some statistics, astronomers found the likelihood that this flare is due to some intrinsic variability in the galaxy as less than 0.01% — one chance in ten thousand. So, very low.
They looked at other potential sources, too, like supernovae, a star getting torn apart by a black hole (!), and even microlensing, but nothing fit the profile.
What does fit, however, is a "small" black hole careening through space at high speed and slamming into the disk of material around the supermassive black hole in the center of J1249. An event like this would create huge shock waves in the disk, causing it to heat up substantially, blasting out radiation for weeks. Gas falling into the smaller black hole would also pile up around it, heat up, and give off a lot of light as well. These are extremely powerful events, releasing about as much energy as the Sun will over its entire lifetime.
Hmmmmm.
OK, you're possibly thinking, so what? What does this have to do with S190521g, the black hole merger that happened a month earlier?
Ah, here's the very fun part. If two black holes of unequal mass merge, the blast of gravitational wave energy is emitted in an asymmetric way: More of it is sent to one side than the other. This produces a huge force on the remnant merged black hole, giving it an extremely powerful kick — remember the energies we're talking about here are vast — and it can be accelerated to high velocities through space.
And if that black hole merger happened near the center of a galaxy, say one with a supermassive black hole and a huge disk of matter swirling around it, then it could cannonball right through that disk at high speed, creating shock waves that could heat the material up and create a gigantic two-month-long flash of light, one bright enough to travel over 4 billion light years and still be seen by a telescope in California.
Incredibly, the math works out. If the gravitational wave event S190521g was from two black holes in the active galaxy J1249 merging to form a single bigger black hole of about 100 times the Sun's mass, the kick from the powerful waves could accelerate it to a staggering velocity of 200 kilometers per second — over 700,000 kilometers per hour! Then, a month or so later this black hole plunged through the disk around the supermassive black hole, and the above events ensue. The amount of energy emitted from such a catastrophe would be about what was seen, and last for as long as the flare from the galaxy.
Holy crap.
This gets better. You need a pair of binary black holes to merge, and black holes form when massive stars explode. But it's hard to make black holes with around 50 times the Sun's mass each (or say 80 and 20). You'd need a star bigger than any we've ever seen. So maybe the two black holes formed separately, from two independent stars, grew over time by eating stuff around them, and then somehow came together to form a binary system later. Good idea, but that's almost impossible to do out in empty space. It's incredibly unlikely, and even then it's hard to get them to orbit one another.
There is a place in the Universe where something like that is way easier, though: Near a supermassive black hole! There can be lots of massive stars orbiting it that turn into black holes, and plenty to feed them. Getting them to orbit one another is easier when there's lot of other stuff around that can nudge them together safely. In fact, it's likely that black holes that massive are themselves the result of mergers of previous black holes. Even if they got one of those off-center kicks, the gravity of the much larger supermassive black hole nearby would keep them from shooting out of the galaxy.
So this story hangs together from start to finish. It actually could be correct.
Now mind you, this is all circumstantial. The math works, and the physics too, but that doesn't mean this is what happened. I was very skeptical when I saw the press release. But reading the paper, I have to think this Rube Goldberg series of events is actually the most likely scenario.
I'd say "incredible" but it's literally credible. Astonishing, certainly.
So the merger didn't produce a flash of light directly, but may have started a series of event what resulted in a whopping huge flash of light a month later. Amazing. And if true, it means this could be happening many times in the Universe, which means we can't just look for immediate flashes from mergers, but also ones that happen weeks or months later.
Incidentally. Given all the physics involved, the astronomers think that the final black hole from the merger is still in orbit around the supermassive black hole, which means it may plunge through the disk again in the future. And not that long, either: Just 1.6 years after the first event, so late 2020/early 2021. You can bet astronomers will keep their telescopic eyes on the galaxy J1249. If the fireworks start up again, we'll have a pretty good guess as to their cause.
A rogue planet apocalypse is another insane thing to think about. This scenario was really brought out in the forefront of public imagination by the 2011 film Melancholia. The film, directed by Lars von Trier, is a psychological drama and sci-fi art film that uses an impending planetary apocalypse as an allegory for severe depression and existential dread. The story in the film is divided into two distinct parts:
• Part One (Justine): Focuses on Justine (played by Kirsten Dunst), who spirals into a deep, paralyzing depressive episode during her lavish wedding reception at a remote castle owned by her sister and brother-in-law. Her marriage quickly unravels as she struggles to perform happiness or meet social expectations.
• Part Two (Claire): Shifts focus to Justine's sister, Claire (played by Charlotte Gainsbourg), and the approaching cosmic threat. A rogue, blue gas giant planet named Melancholia—which initially hid behind the sun—is hurtling on a fatal collision course with Earth.
Theoretically speaking, a rogue planet apocalypse is possible, but the chances are small.
SYFY WIRE
How Worried Should We Be About Rogue Planets Striking Earth?
Almost not at all. Almost.
By: Cassidy Ward
April 6, 2024
Lars von Trier’s 2011 psychological drama, Melancholia, is set against a backdrop of the apocalypse. We watch Justine (Kirsten Dunst) and the people in her orbit collapse into personal chaos as a rogue planet, the titular Melancholia, races toward the Earth.
Justine first notices the effects of the rogue world when a certain star is no longer visible in the sky. Melancholia has emerged from its hiding spot on the other side of the Sun and it’s blocking out distant stars with its rocky body and cloud swept atmosphere; now it’s on a rapid approach to near-Earth space. Experts assure everyone that it will pass by the Earth harmlessly, and it does, but the gravitational tug from the first pass brings it back for a second, more deadly one.
As far as we can tell, there aren’t any rogue planets hiding in the blind spots of our solar system, but there are plenty of rogue planets out there. They are almost impossible to detect and they don’t play by the rules which usually govern planets. Which is enough to make us wonder if von Trier knows something we don’t.
It’s just a planet, but it wears a leather jacket. Planets don’t necessarily have a whole lot in common with one another. Some of them are small and rocky and some are huge and gaseous. Some have moons or rings and others walk their orbital paths alone. Some have thin, wispy atmospheres and others are thick with clouds; still others are naked and barren. The one thing they all have in common is a cozy gravitational relationship with a star. Rogue planets dismiss that planetary requirement too.
A rogue planet’s defining characteristic is that it floats freely through space, untethered to any parent star. That horrifying fate, an entire world kicked out of the nest to wander the cosmos alone, might be way more common than we previously thought. Some rogues probably form independently, the result of a failed star, while others form inside protoplanetary disks around stars, just like the Earth. In the latter case, they are likely ejected from one of a number of intense gravitational events.
A planet might get separated from its family if another star or black hole passes too close to the system. That atypical gravitational nudge might be enough to ripple spacetime in just the right way and fling a planet out of its orbit. Something similar might happen without the influence of a passing star or black hole, during the early days of a stellar system, thanks to something called planetary migration.
When systems are still forming, planets begin coming together wherever the most matter happens to coalesce. As the star, planets, moons, and other cosmic objects grow and collect more mass, they command more of the gravitational landscape and begin to influence one another in new and changing ways. This leads to a chaotic early period during which the planets are in a state of flux. Planets that form in one part of the system can end up in an entirely different part of the system or get kicked out entirely.
Probably not, but it’s hard to say definitively. We know that rogue planets exist and we know that planetary collisions happen. Our own Moon is the product of one such collision between a proto-Earth and a fledgling planet called Theia. The probability of another planetary impact in the future isn’t zero, but it’s probably not worth worrying about.
We find rogue planets primarily through gravitational microlensing. When a rogue planet passes in front of a field of stars, its gravity warps the spacetime around it. Astronomers can tease out a detection from the way starlight bends around the planet as it travels through warped space. The small number of rogue planets we have discovered are far away and in no risk of ever coming anywhere near us. Everything else, the untold number of rogue worlds we haven’t found, that’s all probability.
Attempting to approach a number requires first having some idea of how many rogue worlds are out there and how likely they are to be in any one place (like the same place as the Earth) at any given time. The rough number of rogue planets in our galaxy, let alone the entire universe, is still unknown but one estimate puts it in the trillions. Rogue planets in the Milky Way (and probably in other galaxies, too) might outnumber stars 20 to 1.
They’re out there right now, like lone wolves stalking the dark forest of the cosmos, waiting to pounce. Fortunately for us, that dark forest is pretty dang big and the wolves are wandering aimlessly. Garrett Brown, a celestial mechanics and computational physics researcher at the University of Toronto, estimated the odds of a rogue planet entering the solar system at one in a billion over the next 1,000 years. He puts the odds of it getting as close as the orbit of Mars more like one in a trillion. Pretty long odds.
A separate doomsday possibility with slightly different origins but a similar outcome would be a collision with a planet from our own solar system. It’s possible, over time, that the orbits of one or more planets in the solar system will become unstable. Mercury or Venus might migrate further out or one of the outer planets might snuggle its way in. Regardless of the culprit, the ensuing gravitational chaos could be catastrophic to Earth life even if we didn’t get smacked directly. All of that is unlikely, too.
Our solar system has been stable for billions of years, since pretty shortly after its formation, and it probably will be for a long time yet. While there are limits to how far we can simulate orbits into the future, we’re confident that nothing weird is going to happen for at least tens of millions of years. If you want to hop on the back of another planet’s motorcycle and ride off into the sunset, you’re going to have to come up with another plan. There aren’t any rogue worlds headed our way for the foreseeable future.
But you can live out your doomsday fantasies in Melancholia, streaming now on Peacock.
In the film Melancholia, the physical planet Melancholia acts as a metaphor for depression. While Claire descends into debilitating panic and terror as the end nears, the depressed Justine surprisingly finds a sense of calm and clarity, feeling that the world itself is already corrupt and broken. I've seen the film and the visuals of the rogue planet Melancholia are stunning. The rogue planet is depicted as being significantly larger than Earth—estimated in dialogue and discussions to be roughly 10 to 20 times the size of Earth (with a diameter of at least 66,000 km, making it larger than Uranus). This is a scene from the film, at Justine’s disastrous wedding reception, the ultimate unwanted guest crashes the party, the rogue planet. You can see it lurking in the sky, the tiny blue object to the left.
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The Hiawatha asteroid would have been nearly the size of the comet fragment that slammed into the Atlantic ocean in the 1998 film "Deep Impact." The comet in the film (Wolf-Biederman) was originally 7 miles wide but was broken apart by the nuclear space mission, a 1.5 mile wide fragment of the comet made it's way to Earth and hit the Atlantic ocean, resulting in the famous mega-tsunami scene.
Scientists perform research field work at the edge of the Greenland Ice Sheet while studying the age of the 19-mile-wide (31- km-wide) Hiawatha impact crater that is buried under ice six-tenths of a mile (1 km) thick in 2019.
In the 1998 film Deep Impact, the comet fragment impact generates a wave that is approximately 500 meters (about 1,500 to 1,800 feet) high when it reaches the East Coast and New York City. The initial wave height is roughly 600 feet at the point of impact in the Atlantic Ocean, growing to between 1,500 and 1,800 feet (or around 500 meters) as it slowed and piled up near the coast, towering over skyscrapers and completely submerging landmarks like the Statue of Liberty.
The largest confirmed asteroid to hit Earth is the Vredefort impactor, which struck South Africa about 2 billion years ago. The asteroid is estimated to have been between 20 to 25 kilometers (12 to 15.5 miles) in diameter based on recent studies (previous estimates placed it around 10 to 15 km). It was roughly twice the size of the asteroid that wiped out the dinosaurs (Chicxulub) and occurred long before complex multi-cellular life had evolved. It created the Vredefort Crater, the largest verified impact structure on Earth, with an original estimated diameter of 250 to 300 kilometers (155 to 190 miles), located near what is now Vredefort in the Free State, South Africa. This is the crater from space, you can see the black circular rings that represent the edge of the crater. The Vredefort asteroid impact released an energy equivalent to roughly 6.88 billion Hiroshima atomic bombs detonating simultaneously.
The Manicouagan crater in Québec is a lot older than Chicxulub: 214 million years. Known also as “the eye of Québec”, it became instantly recognizable as an impact crater after flooding of the Manicouagan river by Hydro Québec in the 1960’s. Now anyone can see it on Google Earth and many astronauts, including Canada’s own Chris Hadfield, have photographed it. Manicouagan is the fourth largest impact structure on earth. No tectonic forces have influenced or altered it since its inception. The asteroid hit nearly 1 billion year old Canadian shield rocks. After this event, not much else happened geologically, other than the normal amount of erosion, but it never was an area with high mountains so that wasn’t a whole lot. Then the ice caps of the Quaternary glaciations swept across it, nicely cleaning off debris and making it even more easily visible, so it’s a a rather pure and unchanged. The asteroid responsible for the Crater was approximately 5 kilometers (3 miles) wide.
Manicouagan crater in the winter as photographed from space in 1983.
1.85 billion years ago, a massive asteroid struck Sudbury, Ontario, melting part of Earth’s crust and creating the second-largest confirmed impact crater on Earth, behind only Vredefort in South Africa. 37 million years ago, another asteroid struck nearly the same place. The first impact was enormous. Scientists estimate the asteroid may have been 10–15 kilometers (6-9 miles wide), as big as the asteroid that wiped out the Dinosaurs (Chicxulub). The energy released was so great that vast volumes of rock were instantly melted, forming a huge pool of melted rock within the crater. This was not magma rising from deep inside the Earth. It was the surface rock itself, melted by the force of the collision into what geologists call an impact melt sheet. As that melt slowly cooled, heavy elements separated and concentrated within it, including nickel, copper, palladium, gold, and other platinum-group metals. Instead of remaining scattered through the crust, these materials became gathered and enriched by the cooling melt itself. Dense metal-rich sulfides settled downward, collecting along the base and edges of the structure. In effect, the impact briefly turned this part of Earth into a giant natural smelter, creating the mineral wealth that Sudbury is known for today. Much later, after nearly two billion years of erosion, deformation, and tectonic activity that reshaped the original crater, a second asteroid struck nearly the same place. That impact formed what is now Wanapitei Lake, a circular basin about 8 kilometers across. The younger crater is completely unrelated to the first event. It simply happened to land in terrain already shaped by one of the largest collisions in Earth’s history. Sudbury records two separate cosmic events that reshaped the same landscape, separated by a span of time almost impossible to comprehend.
Theia was a rocky, Mars-sized planetary body (about 5% to 10% of Earth's mass) that shared a similar orbit around the Sun. Theia collided with the early Earth approximately 4.4 billion years ago. The violent impact made the biggest asteroid strikes look like child's play. It blasted a mixture of molten rock and debris from both worlds into orbit, which quickly coalesced to form Earth's Moon. The energy released was approximately 143 trillion times greater than the Tsar Bomba (the most powerful nuclear bomb ever detonated. It released roughly 100 million times more energy than the asteroid impact that wiped out the non-avian dinosaurs. The immense heat and kinetic energy completely melted both bodies (or formed a massive vaporized/molten structure known as a synestia) and liquefied Earth's mantle and surface.
A simulation showing Theia colliding with Earth 4.4 billion years ago.
This book about the Chicxulub asteroid impact always sends chills up my spine every time I look at the cover, the blinding flash of light from the moment the asteroid hit. I mean, the impact produced a blinding, hyper-intense flash equivalent to 100 teratons of TNT (about 4.5 billion times the energy of the Hiroshima bomb or millions of nuclear weapons going off simultaneously). Across the daylight side of the planet, the impact generated an instantaneous, blinding mega-flash that outshone the Sun from regional distances and was visible globally. Even thousands of kilometers away, the sky lit up with extreme thermal radiation capable of causing flash burns, ignition of dry vegetation, and temporary or permanent blindness to any creature looking toward the horizon before the shockwave and ejecta rain arrived.
The Earth is about 7,926 miles (12,756 kilometers) wide at the equator. It is estimated by scientists that it would take an asteroid at least 6 to 10-miles-wide to collapse modern human civilization and an asteroid about 60 to 100-miles-wide to completely sterilize the Earth, boiling away the oceans, melting the crust, and destroying all life on our planet, even deep-subsurface extremophile life. It's just mind-bending to think about it. It's just mind-bending to think that the Earth is so big, and all it would take is a 60 to 100 mile-wide rock to end it all.
And just for clarification, no, a single spacecraft like NASA's DART could not deflect an asteroid as large as the Chicxulub impactor if such an asteroid were headed our way. The DART spacecraft weighed about 550 kilograms (1,210 lbs) and targeted Dimorphos, a small moonlet roughly 160 meters across. In contrast, the Chicxulub asteroid was roughly 10 kilometers (6 miles) in diameter and weighed about a trillion metric tons—roughly 200,000 to 250,000 times more massive than Dimorphos. A kinetic impactor like DART transfers momentum through physical crash force. Crashing a probe into a 10-kilometer-wide mountain of rock would barely register a change in its velocity unless executed millions of years in advance. It would be like a mosquito running into a bus. A massive object like the Chicxulub impactor requires early detection spanning many decades or centuries so a tiny change in speed can accumulate into a wide-enough miss distance by the time it reaches Earth's orbital path. Scientific studies indicate that kinetic impactors alone are inadequate for a 10 km scale threat. Deflecting or fragmenting an object of that magnitude would likely require multiple megaton-class nuclear explosive devices delivered via heavy-lift interplanetary spacecraft. Humanity currently lacks the immediate launch capability, pre-built interceptors, or global coordination needed to deploy a high-megaton nuclear deflection mission on short notice.
We are nowhere close to defending Earth from a cataclysmic asteroid
You can't throw a DART at everything in space.
By: Tom Hartsfield
February 17, 2023
An enhanced photograph of ejected plumes caused by DART’s impact on Dimorphos. (Credit: ASI / NASA / APL)
Last September, NASA smashed a spacecraft into a small asteroid. The results were impressive, as shown in the image above.
The Double Asteroid Redirection Test, or DART, was a success as a prototype technological demonstration. But what can we say about the impact of the mission? What does it mean for our chances of defending the planet from cosmic calamity? Unfortunately, not much — not yet, anyway.
NASA’s DART was a successful mission
The spacecraft performed well. A camera aboard DART captured the scene as the craft passed by Didymos, a near-Earth asteroid. DART’s target was Didymos’ satellite, Dimorphos. The target asteroid expanded to fill the frame, and the test ended abruptly with a head-on strike.
Had the craft hit at a wide angle to the geometric center of the rock, the results could have been different. The asteroid might have rotated or wobbled without slowing its translational motion. (Think of how striking the edge of a billiard ball imparts what competitors call English, while striking the center directs the ball purely forward.) Telescopes detected giant plumes of ejected material thrown out into space, another good sign. Mass sprayed off in one direction imparts force in the other direction on the sprayer.
A few days later, NASA announced that the small asteroid’s orbit around the larger one was altered by an amount large enough to clearly measure. The orbital period dropped by about 32 minutes, from 11 hours and 55 minutes to 11 hours and roughly 23 minutes. This was at the high end of estimates going in, so it is good news.
However, that measurement alone does not tell us how well the tactic would work on an asteroid that poses a real threat — which is what we really want to know. Eventually, NASA will have more complete data, allowing researchers to examine details more carefully. For now, our answers are partial. But we can make further estimates and touch on the science behind asteroid deflection.
Interstellar gnats
A planetary defense mission works by altering the motion of an asteroid by a tiny, tiny amount. Let’s say you rolled two bowling balls down one regulation bowling lane. A gnat flies up the lane and smacks into one of the balls. The impact slows that ball by a miniscule amount, too small to reasonably measure. At the end of the lane, the balls will strike at the exact same time, to the human eye. But if the lane is 1,000 miles long, the gnat-slowed ball will arrive slightly tardy at the far end.
The lanes of space are billions of miles long, so you don’t have to hit the ball very hard if you hit it very far in advance.
Let’s say that by smashing a spacecraft into it, we reduce an asteroid’s velocity by 1/10,000 of 1 percent. The distance it travels in a day might now be reduced from, say, 864,000,000 meters to 863,999,136 meters. So, the asteroid’s expected position slows by 864 meters (0.864 km) each day after the impact. Given that Earth is over 12,000 km in diameter (nearly 8,000 miles), it takes several thousand days for the slow-down to accumulate to its intended effect: namely, allowing Earth to slip past the asteroid.
NASA hoped to slow Dimorphos by about one mile per day. In theory, this would be enough to shift an Earth impact to a near-miss, if the asteroid could be struck ten years plus a few weeks in advance of an impending collision.
What we do not know yet is whether DART’s impact slowed the asteroid more than NASA hoped. We can make some estimates by using the minimal eccentricity of Dimorphos’ orbit about Didymos — which is nearly zero, or circular — the decrease in its orbital period after impact, and NASA’s predictions. In the best-case likely scenario, the impact slowed Dimorphos by about 4 miles per day. In the worst-case likely scenario, it might have slowed it by only one mile per day. The middle-of-the-road estimate is somewhere around 2.5 miles per day. Values outside this are of course possible, and we don’t know enough yet to be sure. These numbers are in line with what NASA hoped for going in, although they are on the high end of expectations.
Re-running our simple calculations, in our best-case outcome, striking Dimorphos 2.5 years in advance would give just enough time to shift an impact trajectory to one that scraped the atmosphere but missed. In the worst case, we would need to impact it ten years ahead of time. How much protection does that afford us?
A nice start, but a long way to go
The Tunguska event was likely caused by a rock about 200 feet across. We can roughly estimate that it had less than 1/20 the mass of Dimorphos. The famous Barringer Crater in the Arizona desert, nearly 600 feet deep, was caused by a similarly sized rock of different composition. Either of these could have destroyed a city unlucky enough to sit at the impact point. Rocks of this size could be effectively deflected by DART less than a year before a predicted strike. The catch is that detecting them is very difficult. Ongoing efforts continue to discover new near-earth asteroids on a nearly daily basis. Objects like the Chelyabinsk meteor in 2013 are often detected only when the fireball lights up the sky.
Dimorphos was discovered in 2003. If it had been on a collision course for, say, 2030, we could probably prevent an impact. Didymos, about which it orbits, was discovered in 1996.
This is where the bad news starts.
Let’s say that Didymos was due to hit Earth. Its diameter is about 4.5 times that of Dimorphos. That means Didymos has something like 95 times more mass. In this case, DART would have to impact it somewhere between 190 and 950 years in advance to alter its course sufficiently. We only discovered it 26 years ago. If we needed to deflect it within a few years, we would have to hit it 100 times harder than DART hit Dimorphos. That means mass and velocity, multiplied together, must be on a scale 100 times greater than that of DART. This is possible, but it would stretch our current capabilities. We could add mass through a series of large launches, perhaps using Falcon Heavy launch vehicles. Additional engines could be launched to boost velocity. As for rocks larger than Didymos, they would pose a much greater problem.
The famous Chicxulub impactor that caused a mass extinction 66 million years ago was roughly 10,000 meters in diameter. The mass of this object — about 200,000-fold greater than Didymos — was significant enough that a spacecraft like DART would have to impact it millions of years in advance to avoid an extinction-level impact. No conceivable improved version of DART is capable of preventing such an event. For that, we would need far more powerful countermeasures. An investigation of this problem was carried out by scientists T.J. Ahrens and A.W. Harris, who analyzed the necessary countermeasures against asteroids of varying sizes. For small rocks, they conclude that a mission like DART, perhaps scaled up a bit, could be enough — as DART indeed just showed.
For rocks bigger than Didymos, but much smaller than Chicxulub, the impactor would need thousands of times more momentum. We cannot easily make a craft thousands of times faster or thousands of times more massive than DART with current rocketry technology. Nuclear weapons could impart enough push to do the job, with certain careful considerations about the composition of the asteroid, the location of the blast, how well the blast could be directed, the amount of ejecta blasted away, and so forth.
For giant objects like Chicxulub, the only presently feasible option is a truly enormous nuclear blast. A device of many megatons might give us a chance. Fortunately, we are likely to spot asteroids of this size far in advance.
DART was a useful first step toward asteroid deflection capability. However, Dimorphos is very small. We have a long way to go before we can defend against truly catastrophic collisions.
And also just to clarify, no, a standard Chicxulub-sized asteroid cannot "sneak up" on Earth. Because an object of that scale (10 to 15 kilometers wide) is incredibly massive and reflects a significant amount of light, automated planetary defense telescope systems have already mapped and tracked virtually 100% of all Near-Earth Asteroids (NEAs) of this size. Astronomers can calculate their orbits centuries into the future, and none are currently on a collision course with Earth. However, there are two extreme, highly unlikely astronomical scenarios where a planet-killer could catch us with limited warning:
The most significant limitation of Earth's current ground-based optical telescopes is the glare of the Sun. If a previously unknown, highly eccentric asteroid approached Earth directly out of the Sun's direction, it could remain hidden in the daylight sky until it was very close. Even so, because a 10 km object is so large, we would still likely spot it weeks or months in advance as it crossed the inner solar system, rather than discovering it only hours before impact.
The real "wild card" is not a local asteroid, but an object originating from the outermost edges of our solar system (the Oort Cloud) or from another star system entirely.
• Long-Period Comets: These giant chunks of ice and rock spend thousands of years in deep space where they are completely dark and invisible to us. If one shifted into an Earth-crossing orbit, it would travel at extreme speeds.
• Warning Time: We would only detect it once it grew close enough to the Sun to start heating up and forming a visible tail. For an object that massive, we might only get a few months to a couple of years of warning before impact—which, as established, is not enough time for humanity to mount a successful deflection mission.
In summary, the odds of an asteroid the size of the Chixculub impactor sneaking up on us are effectively zero. The odds of a giant, undetected comet appearing out of the deep outer solar system on a direct collision course are mathematically real, but extraordinarily rare, happening only once every tens or hundreds of millions of years.
The History Channel did a 10-part series called "Doomsday: 10 Ways the World Will End", most of it is available on YouTube for viewing. It interviews some of the world's best physicists, paleontologists, and experts and discusses the many threats to our existence, asteroids, Black holes, Gamma Ray bursts, Supervolcanoes, Nuclear War, rogue planets, and even our own sun. Being interested in space, science, physics, and almost everything about life in general, you can't help but wonder how it will all come to an end.
Gamma-ray bursts are quite insane to think about. A gamma-ray burst (GRB) cannot physically blow up or destroy the planet Earth, but a close enough hit could wipe out most life on the surface. A GRB is a hyper-energetic cosmic explosion from a collapsing massive star or merging neutron stars. It releases more energy in a few seconds than our Sun will produce in its entire lifetime. The energy shoots out in narrow, intense beams from the poles of the exploding or merging object. If a beam directly targeted Earth from within a few thousand light-years, the high-energy photons would tear apart nitrogen and oxygen molecules in the upper atmosphere. This destroys the ozone layer. With the ozone layer gone, intense ultraviolet (UV) radiation from the Sun would flood the surface. The ozone layer acts as a global shield by absorbing dangerous solar ultraviolet (UV-B and UV-C) rays. If a nearby gamma-ray burst (GRB) stripped away or severely thinned this layer, that barrier would vanish and our skin would be left completely exposed to the hellish wrath of the sun's radiation. This could also trigger massive ecological collapse, plant and marine die-offs, and a mass extinction event. Some scientists suggest a GRB may have contributed to a past extinction, such as the Ordovician mass extinction 450 million years ago. To cause a mass extinction, the GRB would need to occur relatively close within our own galaxy—typically estimated within a few hundred to a few thousand light-years. According to the European Space Agency, there are no known candidate stars capable of producing a GRB close enough to threaten Earth (with safe zones generally falling within 200 to several thousand light-years). Distant bursts are harmless. Billions of light-years away, GRBs like the record-setting "BOAT" burst observed by NASA/ESA only slightly ionize Earth's upper ionosphere without posing any danger to life on the ground.
Effect of a gamma ray burst on an Earth-like planet.
You know, it's fascinating. The famous and legendary astrophysicist Neil degrasse Tyson once said that if he could choose a way to die, he would like die by falling into a black hole. He stated he would choose falling into a black hole as his preferred way to die because it serves as the ultimate cosmic experiment, allowing him to experience intense relativistic physics and transmit data back to scientists before being destroyed. He views it as a rare opportunity to gather data from an extreme gravitational environment that cannot be replicated in a terrestrial laboratory. He has described the process of falling feet-first, where the gravitational pull on your feet is much stronger than on your head, stretching and compressing the body into a stream of particles—a phenomenon known as spaghettification. He noted that, in theory, an observer equipped with specialized transmitters could relay information back to scientists outside the event horizon before crossing the point of no return. Due to extreme gravitational time dilation, time passes differently near a black hole compared to the rest of the universe, offering a surreal window into cosmic mechanics. Black holes are extremely mysterious and complex.... and quite terrifying. Contrary to popular myth, black holes do not suck things in like a cosmic vacuum cleaner, black holes pull objects using normal gravity, not a mysterious suction force. A black hole exerts the exact same gravitational pull as any other star or object of the same mass. If the Sun were suddenly replaced by a black hole with the exact same mass, the Earth would not get sucked in; it would continue orbiting safely in the same path. Danger only begins when an object gets too close and crosses an invisible boundary called the "event horizon", two of the scariest words in science. This is the "point of no return" where the gravitational pull becomes so strong that nothing—not even light—can escape. Objects do not automatically fall in. Planets, gas, and stars can safely orbit black holes if they keep enough distance or have enough sideways speed. If something gets too close to the event horizon, extreme gravitational differences between the front and back of the object stretch it out like a strand of spaghetti, the spaghettification process. A black hole is a region in space where a massive amount of matter is packed into a tiny space, creating a gravitational pull so strong that nothing—not even light—can escape its bounds. The "event horizon" is the invisible boundary surrounding a black hole, it is the point of no return, once anything crosses it, it cannot break free from the gravity. The "singularity" is the center of a black hole where matter is crushed down to a point of infinite density and zero volume, where the laws of physics completely break down. The "accretion disk" is a swirling ring of superheated gas, dust, and debris that often orbits around a black hole, glowing brightly in X-rays and other light wavelengths. There are four main types of black holes.
• Stellar-mass Black Holes (up to a few dozen solar masses): Formed when a giant star runs out of fuel and collapses under its own weight in a supernova.
• Supermassive Black Holes (millions to billions of solar masses): Massive giants located at the centers of nearly all large galaxies, including Sagittarius A* at the heart of the Milky Way.
• Intermediate-mass Black Holes (hundreds to thousands of solar masses): A rarer, mid-sized category whose exact formation remains under scientific study.
• Primordial Black Holes (theoretical): Tiny, hypothetical mini black holes proposed to have formed during the first moments after the Big Bang.
The strength of gravity inside a black hole is infinite at its absolute center (the singularity), but its pull depends entirely on how close you are to it. From a distance, a black hole has the exact same gravitational pull as any normal object of the same mass. If our Sun were replaced by a black hole with the exact same mass, Earth would not get sucked in—it would continue to orbit normally (though it would be very cold). The extreme, inescapable gravity only happens when you get too close. Gravity depends on mass and distance. Because a black hole packs massive amounts of matter into a tiny, compressed point, you can get incredibly close to its entire mass. As you approach a black hole, you reach the "event horizon." At this precise boundary, the gravity becomes so strong that the escape velocity (the speed required to break free) exceeds the speed of light. Since nothing can travel faster than light, absolutely nothing—not even light itself—can escape once it crosses this line. If you were to fall into a black hole feet-first, the gravity pulling on your feet would be vastly stronger than the gravity pulling on your head. This extreme difference in gravitational force over a short distance is called a tidal force. It would stretch an object out horizontally and pull it vertically, a real scientific phenomenon colorfully known as spaghettification. Yes, if Earth got too close to a black hole, spaghettification would absolutely occur. The planet would be stretched, torn apart, and eventually swallowed as a stream of debris. However, how and when this happens depends entirely on the size of the black hole.
Scenario 1: A Stellar-Mass Black Hole (The Violent Stretch)
If Earth approached a smaller black hole (about 5 to 30 times the mass of our Sun), the tidal forces would strike long before the planet even reached the event horizon. The gravity on the side of Earth closest to the black hole would be thousands of times stronger than the gravity on the far side. This massive difference in pull would overcome the internal gravity holding Earth together. The result, Earth would be violently ripped into a long, thin stream of rock, magma, and gas, resembling a cosmic noodle before crossing the threshold.
Scenario 2: A Supermassive Black Hole (The Hidden Trap)
If Earth approached a supermassive black hole (like the ones at the center of galaxies, millions of times the mass of our Sun), a strange quirk of physics occurs. Because the black hole is so enormous, its event horizon is massive, and the tidal forces at the edge are surprisingly gentle. Earth could actually cross over the event horizon intact without being spaghettified yet. Once inside, however, Earth would be completely trapped in the region of inescapable gravity. As Earth continued its plunge toward the central singularity, the gravity would intensify exponentially. Spaghettification would still happen, but it would take place inside the black hole, hidden from the rest of the universe.
What We Would Experience First
Long before the physical rock of Earth stretched into a noodle, the atmosphere and oceans would be stripped away. Extreme earthquakes, super-volcanoes, and catastrophic tidal waves would tear across the surface as the black hole's gravity began to warp the planet's shape.
Theoretically speaking, yes, a black hole could enter our solar system and end the world. While space is mostly empty and the chances are incredibly small, there is no law of physics that prevents a wandering black hole from passing through our cosmic neighborhood. A black hole wouldn't even need to swallow Earth directly to destroy life as we know it. Depending on its size and path, its entry into our solar system could end the world in a few different ways.
Scenario 1: A Wandering Stellar Black Hole (Gravitational Chaos)
Most black holes are "stellar-mass" black holes, created from collapsed stars. They can drift through the galaxy undetected because they don't emit light unless they are actively feeding.
If one passed through our solar system, its massive gravitational pull would act like a cosmic bowling ball scattering pins:
• Orbits Destabilized: It would alter the orbits of the planets. Earth could be pulled closer to the Sun, scorching the surface, or flung further away into freezing deep space.
• Flung Out of the Solar System: Earth could be entirely ejected from the solar system, turning us into a frozen, dark "rogue planet" where life could not survive.
• Asteroid Showers: The black hole would disturb the Oort Cloud and Kuiper Belt (the icy regions at the edge of our solar system), sending millions of massive comets and asteroids hurtling directly toward the inner planets.
Scenario 2: A Rogue Supermassive Black Hole (Instant Obliteration)
Supermassive black holes stay at the centers of galaxies. However, when galaxies collide, these monsters can occasionally be kicked out into deep space.
• If a supermassive black hole entered our solar system, its gravity is so overwhelming that it wouldn't just disrupt orbits—it would swallow the Sun and all the planets whole.
• The solar system would simply cease to exist in a matter of days or weeks.
Scenario 3: A Micro "Primordial" Black Hole (The Silent Bullet)
Scientists have theorized that tiny black holes, the size of an atom but with the mass of a mountain, could have formed during the Big Bang.
• If a micro black hole passed through Earth, it would act like an unstoppable, hyper-dense bullet.
• It would shoot right through the planet from one side to the other in minutes.
• While it might not swallow the Earth, the energy released by its passage could trigger catastrophic, global earthquakes and volcanic eruptions.
The Real-World Reality Check
While this is a terrifying theoretical concept, astronomers actively track the movements of nearby stars and cosmic structures. There are currently no known black holes anywhere near our solar system, and space is so vast that the probability of one colliding with us is practically zero in our lifetime. This is a fascinating interview with astronomer Phil Plait about a black hole apocalypse.
Could the Earth Be Destroyed by a Black Hole?
If a black hole came wandering through the solar system, would we notice? We're joined by the Bad Astronomer, Dr. Phil Plait, to chat about the possibility of Earth meeting its end via gravitational catastrophe.
Transcript
ERIC: From the Museum of Science in Boston, this is Pulsar, a podcast where we search for answers to the coolest questions we've ever gotten from our visitors. I'm your host, Eric. And today we're going to put our planet in peril by answering a question we get with surprising frequency. Could the earth ever be destroyed by a black hole? Joining me is the person I usually think of when I'm contemplating planetary annihilation: the Bad Astronomer, Dr. Phil Plait, author of Death From the Skies: These Are the Ways the World Will End. Dr. Plait, thanks so much for being here on Pulsar.
PHIL: Oh my pleasure, I'm really happy to support the museum.
ERIC: So it turns out a lot of people ask us this question only having heard of black holes as awesome, powerful things in space, and not really knowing what they are. So can we start with an overview of what makes a black hole a black hole?
PHIL: Sure! What makes a black hole a black hole is its intense gravity. The gravity that you feel from an object depends on two things: how much stuff is in that object - how much mass it has, and how close you are to it. And if you take a lot of mass and squeeze it into a smaller and smaller volume, you can get closer and closer to it, because it's smaller. And when that happens, the gravity gets stronger and stronger. And at some point, if you have enough mass squeezed into a tiny enough volume, you get a black hole. Black holes have really, really, really strong gravity.
ERIC: Yeah that Hollywood, maybe like, general perception of a black hole being a hole that opens in space: not really true, it's just really powerful gravity. It still can do a lot of annihilation, but it's not something that's going to just appear somewhere, like, right next to the earth.
PHIL: And the power of the black hole comes from the fact that its gravity gets more intense the closer you are to it. And if you're heading towards the sun, there's only so close you can get to the sun before you kind of smack into its surface. And that's the most gravity you can feel. But if you take the sun and then compress it down into a ball that's just a few miles across. Yeah, it becomes a black hole, you can keep getting closer and closer to it, instead of being basically 400,000 miles from the center or something like that, you can get much, much, much closer, you can just be a few miles from the black hole. And so the gravity you feel is really, really strong. And that's where their destructive power comes from.
ERIC: Now we get that question a lot, too. What would happen if the sun magically turned into a black hole?
PHIL: Now gravity fades with distance. Replace the sun with a black hole, we wouldn't even really notice. I mean, we'd freeze, right? We wouldn't be getting light and heat. But the gravity we'd feel from the Sun is the same because the mass of the Sun stays the same. And we're the same distance from it. That's the critical thing. So if you take a black hole and put it really far away, you don't feel that much from it.
ERIC: Okay, so distance is a factor. But if one got closer, could a black hole destroy the Earth?
PHIL: And I want to be careful here, because I get this question a lot, too. And let me say, can a black hole destroy the Earth? Yes. Will a black hole destroy the Earth? Probably not. You know, you never say no. Because you have to kind of qualify it and say, look, there are a lot of black holes in the Milky Way galaxy, millions and millions of them really, and that sounds terrifying. But space is big. And that's why we call it space. And they're really, really, really far away. And if you do the math, it's actually fairly complicated. How often would a black hole get close enough to the sun into the earth to do damage? And the answer is essentially never, over the entire age of the universe. This probably has not happened. If it had happened, we wouldn't be here. So you know, right away that tells you over 4 billion years it hasn't happened, even once.
ERIC: So nothing to lose sleep over, which is great. But say one did wander into the solar system. What kind of things would we notice first?
PHIL: So if we pretend that this will happen, and again, probably not, but if it were to happen, your typical black hole, which is 10 or 20 times the mass of the Sun, is very small. It's only a few dozen miles across, and it's black, so it doesn't emit light. And if it's just out there in space, we won't see it. Now it may have some effect on starlight. Starlight passes it, it gets bent and warped. And we might notice that, that would be that would be pretty cool, although terrifying. But the effect it would have gravitationally on us would first probably be with the outer planets or even these chunks of ice and rock that orbit the Sun even out past Neptune. These are like gigantic comets and the gravity of the black hole would probably disturb those. And we see these things falling in towards the sun and think, Wow, we're getting a lot of comets lately, what's going on with that? Oh, maybe it's a black hole. And then as it gets closer, the orbits of the planets would change. And we'd see that because we know how the planets go around the sun. And then if it got close enough to Earth, then it would be bad. The moon might get pulled out of its orbit. And then there are the tides. Gravity changes with distance. The closer you are to something, the stronger the gravity. And if one side of the Earth is closer to the black hole than the other side, that means that there's a different force on the two sides of the earth. And that will stretch us like an egg. And if the black hole gets close enough, it will tear the earth apart.
ERIC: Sounds like all kinds of bad things could happen if a black hole were to wander by, but as you said, space is really big. What is the closest one that we know of to the earth?
PHIL: That's a hard question to answer. In fact, for a long time, it was this one called Cygnus X one that's over 1,000 light years away. There is one recently discovered, which I'm going to put in air quotes, which is closer, but it's not convincing that it's a black hole just yet. The problem is because they're black, we can't see them directly. But if they're orbiting a star, we can see their effects on the star. And it's not clear that what we're seeing going on with the star is actually because of a black hole.
ERIC: But still not really in our neighborhood. 1,000 light years away, that's really far. And that's not gonna affect us anytime soon, or ever.
PHIL: That's correct. For something to have an actual effect on us, it would have to be certainly no farther than a light year away. If we're talking about sort of a normal black hole that we we talk about when a star explodes and the core collapses, and it forms what we call a stellar mass black hole, it would have to be pretty close. And the odds of that happening are extremely rare. Think of it this way: there are hundreds of billions of stars in the galaxy, thousands of times more stars than there are black holes. And yet a star has never really passed close enough to the Earth to damage us over the four and a half billion years we've been around. So the odds of a black hole getting closer are a thousand times worse. So I'm not too concerned about it.
ERIC: Now, black holes don't show up too often in science fiction, but you got your nickname by pointing out the bad astronomy in movies, like nonsense with moon phases not changing, or magical orbits on space stations that have unexplained gravity. So I have to ask, are there any particularly bad or good representations of black holes from popular films?
PHIL: Yeah, if you watch Disney's The Black Hole from the 1970s, it's not great. But the movie Interstellar, which came out a few years ago, and I'll preface this with saying, I didn't care for it, not my cup of tea, but the representation of black holes, it was done very well. They talk about the intense gravity, they talk about how black holes can spin, they talk about the tides from a black hole. And they also talked about, and this was an important part of the movie, time dilation. The closer you get to a black hole, and the stronger the gravity is, your clock ticks slower. Time flows more slowly for you compared to somebody really far away from the black hole. And that's a real effect. It's not like a mechanical thing where your watch is just slowing down. Time literally moves more slowly. Not only was that depicted fairly well in the movie, it was a plot point. And it was kind of kind of an important thing that happened there. So that was pretty neat. And also just the visual representation of the black hole. The way light bends around it. That was all done really really well.
ERIC: Alright, so it sounds like we shouldn't lose any sleep over black holes. But that doesn't mean we shouldn't keep studying them because they they do sound pretty awesome. And they do sound like some of those powerful forces in the universe.
PHIL: That's correct.
ERIC: All right, Dr. Plait. Thanks so much for joining us here on Pulsar.
PHIL: Thank you.
ERIC: For more awesome and terrifying things that could destroy entire planets, come talk to our staff at the Charles Hayden Planetarium at the Museum of Science. And be sure to check out Death From the Skies: These Are the Ways the World Will End. wherever science-y books are sold. Until next time, keep asking questions.
One of the greatest scenes in film history, Interstellar, Joseph Cooper enters the supermassive black hole named Gargantua. Gargantua is a massive, rapidly spinning black hole that dominates the planetary system visited by the crew. After performing a gravitational slingshot maneuver with the spacecraft, Cooper detaches from the main ship and falls past the event horizon into Gargantua. Inside, he enters a physical manifestation of five-dimensional space known as the Tesseract, allowing him to send quantum data back to Earth via his daughter Murphy Cooper. I just about fell off of my sofa the first time I watched this scene.
Joseph Cooper enters the black hole Gargantua.
It's fascinating, scientists have directly imaged two individual supermassive black holes using the Event Horizon Telescope, alongside the first radio image of a binary black hole system. The observations for the first direct black hole images were taken in April 2017 by the Event Horizon Telescope network:
• Messier 87 (M87)* (the supermassive black hole in the M87 galaxy): The data was captured in April 2017 and the historic first image was publicly released on April 10, 2019.
• Sagittarius A* (the supermassive black hole at the center of the Milky Way): The data was also captured in April 2017 (though processing took longer due to data shipment from the South Pole), and the image was publicly released on May 12, 2022.
Folks, I don't think people understand just how big black holes can get. It's mind bending. The largest known and reliably measured black hole in the universe is TON 618, though Phoenix A is theorized to be larger. TON 618 is estimated at 66 billion times the mass of our Sun (some lower recent estimates place it around 40.7 billion solar masses). It is a hyperluminous, radio-loud quasar. Its event horizon is so large that it spans roughly 390 billion kilometers, meaning entire solar systems could fit inside it comfortably. It sits approximately 18.2 billion light-years away from Earth.
This is what a black hole looks like in space without it's accretion disk, very eerie. Black holes only have accretion disks if they are accreting, actively feeding on gas and dust. Scientists find black holes indirectly by observing how their immense gravity and physical processes affect nearby matter, light, and spacetime. Because black holes do not emit or reflect light, astronomers use several key methods to detect them:
• Stellar Orbital Dynamics: Astronomers watch stars orbiting an invisible, super-dense point in space. By tracking their speed and paths, scientists calculate the hidden mass using gravity laws. This method confirmed Sagittarius A* at the center of the Milky Way.
• Accretion Disk X-rays: When a black hole pulls gas and dust from a companion star, the matter forms a spinning disk called an accretion disk. Friction heats the gas to millions of degrees, causing it to glow and emit high-energy X-rays that space telescopes can capture.
• Gravitational Waves: When two black holes spiral together and merge, they send violent ripples through the fabric of space-time. Instruments pick up these waves to measure the masses of the colliding bodies.
• Gravitational Lensing: A black hole's strong gravity bends and magnifies light coming from a star or galaxy directly behind it. This distortion reveals isolated or wandering black holes that would otherwise stay hidden.
• Direct Shadow Imaging: Global networks of radio telescopes, such as the Event Horizon Telescope (EHT), link together to capture the dark shadow of a black hole silhouetted against its glowing ring of superheated plasma (such as in M87 and the Milky Way center).
You see this image on Facebook a lot, an AI generated image of what it would look like from Earth if a black hole were approaching. This is complete fiction. While the design of the black hole itself is highly accurate—modeled after the iconic "Gargantua" from the sci-fi movie Interstellar—the depiction of it looking like this in Earth's sky is scientifically impossible. If a black hole large enough to be resolved by the naked eye were actually this close to Earth, the reality would look vastly different. The Atmosphere and Earth would already be destroyed. Before a black hole could ever get this visually large in the sky, its immense gravitational and tidal forces would completely pull apart the Earth. Long before it reached this point, the atmosphere would be stripped away, and the planet would experience catastrophic earthquakes, global volcanism, and spaghettification. There would be no houses or telephone poles left standing to view it from. A real black hole doesn't just sit perfectly on top of a sunset sky. Because its gravity is so intense, it acts as a massive lens. It would warp, stretch, and duplicate all light passing behind it, completely distorting the horizon, the stars, and the sky surrounding it into chaotic rings and arcs of light. The glowing orange ring you see is the accretion disk, made up of superheated gas and dust spinning at near light-speed. The extreme X-rays and gamma radiation radiating from this disk would completely strip away Earth's ozone layer and atmosphere, vaporizing life on the surface and sterilizing the planet. The accretion disk of a black hole typically reaches temperatures from 1 million to over 100 million Kelvin (roughly 1.8 million to 180 million degrees Fahrenheit), with inner hot regions and surrounding coronae climbing even higher.
Love this up close image of a black hole. This is a remarkably realistic depiction of a black hole, though it includes a few specific compromises made for cinema. This image shows Gargantua, the fictional supermassive black hole created for Christopher Nolan’s 2014 film Interstellar. Rather than hiring artists to guess what it would look like, the visual effects team collaborated with Nobel Prize-winning theoretical physicist Kip Thorne. They fed actual mathematical equations from Einstein’s Theory of General Relativity into custom rendering software. The simulation was so precise that the team actually published peer-reviewed astrophysics papers about what they discovered during rendering.
Stunning visual of the black hole Gargantua from the film Interstellar. The glowing accretion disk and warped light around the black hole. Gravitational lensing bends the light of the disk both above and below the black hole's shadow, creating the bright, halo-like ring appearance.
Here is a graph showing the location of the event horizon and singularity of a black hole.
The giant waves on Miller’s planet in the film Interstellar were caused by the extreme gravitational tidal forces of the supermassive black hole, Gargantua. Because the planet orbited dangerously close to Gargantua, the black hole's gravity pulled intensely on the planet's oceans. Instead of normal rolling ocean waves, the water was deformed into massive, permanent tidal bulges (up to 4,000 feet or roughly 1,200 meters high). Rather than rotating smoothly, the planet experienced a wobble or back-and-forth balance as it orbited. This motion caused the giant bulges to "slosh" across the shallow ocean roughly once every hour. Because most of the planet's water was tied up in these towering bulges, the rest of the ocean stayed very shallow (only knee-deep where the crew landed), making the passing wave look like a towering, moving wall. Another phenomenal scene.
A binary black hole is an astronomical system made of two black holes that orbit closely around a shared center of gravity. These systems are generally divided into two main categories:
• Stellar-mass binary black holes: Formed from the remnants of massive binary star systems that separately collapse into black holes, or created through dynamic encounters and mutual capture in dense star clusters.
• Supermassive binary black holes: Involve giant black holes with millions or billions of solar masses, believed to form when two galaxies merge.
As the two black holes spiral closer and closer together, they distort space-time and release immense amounts of energy in the form of gravitational waves—ripples in the fabric of the universe predicted by Albert Einstein. Eventually, the two black holes collide, essentially eating each other, and merge into a single, larger black hole. Scientists first directly detected a binary black hole merger in 2015 using observatories like LIGO, opening a new era of gravitational-wave astronomy. This is a great article about their behavior.
Bad Astronomy
Merging black holes blast out light… but not for the reason you'd think
By: Phil Plait
Jun 26, 2020
A binary pair of black holes about to merge together, near the huge disk of material swirling around a supermassive black hole in a distant active galaxy. Credit: Caltech/R. Hurt (IPAC)
When two black holes eat each other, they release a lot of energy.
A lot. A significant fraction of the mass of the black holes is converted into energy, radiating away as gravitational waves, ripples in the fabric of spacetime. These can have as much energy as — and I am not kidding you here — tens of thousands of times as much as the Sun will radiate over its entire lifetime… and they blast away in a few seconds. Put another way, during that time the black holes emit hundreds of millions of times more energy than all the stars in the galaxy combined.
That kind of power is terrifying. Mind crushing. Yet, for all that, the event itself is entirely invisible, giving off no light at all. It's possible under some specific circumstances some light will be emitted, but generally speaking the two black holes merge, scream out their gravitational waves, and become a single, somewhat larger black hole… and all this without a photon emitted.
So no light is produced directly. But indirectly, it turns out things can be different.
Artwork depicting two black holes orbiting each other, shortly before they merge and blast out gravitational waves. Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)
On 21 May, 2019, the LIGO and Virgo gravitational wave observatories detected a pair of black holes merging somewhere in the Universe — the event was given the designation S190521g. Triangulating the signal, it was found to come from a spot in the sky the direction of the constellation Coma Berenices. Within moments, an automated alert was sent out to telescopes all across the planet to look for some sort of optical signal.
No flash of light was seen. At least, not right away.
On Mt. Palomar in California there is a 1.2-meter telescope with a 600 megapixel camera that can see a whopping 47 square degrees of sky at a time, a huge field of view. Called the Zwicky Transient Facility it scans the sky looking for things that go flash (or just change brightness) in the night.
34 days after the LIGO-Virgo gravitational wave detection, it was looking toward Coma Berenices and saw a flare, a brightening, coming from the distant galaxy AGN J124942.3 +344929 (let's call it J1249 for short). This is an active galaxy, one with a supermassive black hole in its heart (with a mass of 100 million times the Sun, so decently huge) that's actively eating material. As it falls in, this material gets very hot and emits quite a bit of light, making this galaxy visible even from its forbidding distance of 4.6 billion light years.
The flare detected lasted for about 50 days. Over that time, the amount of energy it emitted was huge, about 1044 Joules — more energy than the Sun will emit over its entire lifetime!
A month after a pair of black holes merged, a huge flare of light was released from the galaxy AGN J124942.3 +344929 (arrowed), possibly as the merged black hole interacted with material around a third supermassive black hole. Credit: Aladin / DSS
Active galaxies are known to flare, but this particular one had been quiet, or at least had a steady luminosity, for a year around the flare. Looking at the galaxy's history (and the histories of other galaxies) and applying some statistics, astronomers found the likelihood that this flare is due to some intrinsic variability in the galaxy as less than 0.01% — one chance in ten thousand. So, very low.
They looked at other potential sources, too, like supernovae, a star getting torn apart by a black hole (!), and even microlensing, but nothing fit the profile.
What does fit, however, is a "small" black hole careening through space at high speed and slamming into the disk of material around the supermassive black hole in the center of J1249. An event like this would create huge shock waves in the disk, causing it to heat up substantially, blasting out radiation for weeks. Gas falling into the smaller black hole would also pile up around it, heat up, and give off a lot of light as well. These are extremely powerful events, releasing about as much energy as the Sun will over its entire lifetime.
Hmmmmm.
OK, you're possibly thinking, so what? What does this have to do with S190521g, the black hole merger that happened a month earlier?
Ah, here's the very fun part. If two black holes of unequal mass merge, the blast of gravitational wave energy is emitted in an asymmetric way: More of it is sent to one side than the other. This produces a huge force on the remnant merged black hole, giving it an extremely powerful kick — remember the energies we're talking about here are vast — and it can be accelerated to high velocities through space.
And if that black hole merger happened near the center of a galaxy, say one with a supermassive black hole and a huge disk of matter swirling around it, then it could cannonball right through that disk at high speed, creating shock waves that could heat the material up and create a gigantic two-month-long flash of light, one bright enough to travel over 4 billion light years and still be seen by a telescope in California.
Incredibly, the math works out. If the gravitational wave event S190521g was from two black holes in the active galaxy J1249 merging to form a single bigger black hole of about 100 times the Sun's mass, the kick from the powerful waves could accelerate it to a staggering velocity of 200 kilometers per second — over 700,000 kilometers per hour! Then, a month or so later this black hole plunged through the disk around the supermassive black hole, and the above events ensue. The amount of energy emitted from such a catastrophe would be about what was seen, and last for as long as the flare from the galaxy.
Holy crap.
This gets better. You need a pair of binary black holes to merge, and black holes form when massive stars explode. But it's hard to make black holes with around 50 times the Sun's mass each (or say 80 and 20). You'd need a star bigger than any we've ever seen. So maybe the two black holes formed separately, from two independent stars, grew over time by eating stuff around them, and then somehow came together to form a binary system later. Good idea, but that's almost impossible to do out in empty space. It's incredibly unlikely, and even then it's hard to get them to orbit one another.
There is a place in the Universe where something like that is way easier, though: Near a supermassive black hole! There can be lots of massive stars orbiting it that turn into black holes, and plenty to feed them. Getting them to orbit one another is easier when there's lot of other stuff around that can nudge them together safely. In fact, it's likely that black holes that massive are themselves the result of mergers of previous black holes. Even if they got one of those off-center kicks, the gravity of the much larger supermassive black hole nearby would keep them from shooting out of the galaxy.
So this story hangs together from start to finish. It actually could be correct.
Now mind you, this is all circumstantial. The math works, and the physics too, but that doesn't mean this is what happened. I was very skeptical when I saw the press release. But reading the paper, I have to think this Rube Goldberg series of events is actually the most likely scenario.
I'd say "incredible" but it's literally credible. Astonishing, certainly.
So the merger didn't produce a flash of light directly, but may have started a series of event what resulted in a whopping huge flash of light a month later. Amazing. And if true, it means this could be happening many times in the Universe, which means we can't just look for immediate flashes from mergers, but also ones that happen weeks or months later.
Incidentally. Given all the physics involved, the astronomers think that the final black hole from the merger is still in orbit around the supermassive black hole, which means it may plunge through the disk again in the future. And not that long, either: Just 1.6 years after the first event, so late 2020/early 2021. You can bet astronomers will keep their telescopic eyes on the galaxy J1249. If the fireworks start up again, we'll have a pretty good guess as to their cause.
An artists rendition of what it would look like if Earth got too close to a black hole. The planet would literally be ripped apart by the gravity.
Two great documentaries about black holes.
A rogue planet apocalypse is another insane thing to think about. This scenario was really brought out in the forefront of public imagination by the 2011 film Melancholia. The film, directed by Lars von Trier, is a psychological drama and sci-fi art film that uses an impending planetary apocalypse as an allegory for severe depression and existential dread. The story in the film is divided into two distinct parts:
• Part One (Justine): Focuses on Justine (played by Kirsten Dunst), who spirals into a deep, paralyzing depressive episode during her lavish wedding reception at a remote castle owned by her sister and brother-in-law. Her marriage quickly unravels as she struggles to perform happiness or meet social expectations.
• Part Two (Claire): Shifts focus to Justine's sister, Claire (played by Charlotte Gainsbourg), and the approaching cosmic threat. A rogue, blue gas giant planet named Melancholia—which initially hid behind the sun—is hurtling on a fatal collision course with Earth.
Theoretically speaking, a rogue planet apocalypse is possible, but the chances are small.
SYFY WIRE
How Worried Should We Be About Rogue Planets Striking Earth?
Almost not at all. Almost.
By: Cassidy Ward
April 6, 2024
Lars von Trier’s 2011 psychological drama, Melancholia, is set against a backdrop of the apocalypse. We watch Justine (Kirsten Dunst) and the people in her orbit collapse into personal chaos as a rogue planet, the titular Melancholia, races toward the Earth.
Justine first notices the effects of the rogue world when a certain star is no longer visible in the sky. Melancholia has emerged from its hiding spot on the other side of the Sun and it’s blocking out distant stars with its rocky body and cloud swept atmosphere; now it’s on a rapid approach to near-Earth space. Experts assure everyone that it will pass by the Earth harmlessly, and it does, but the gravitational tug from the first pass brings it back for a second, more deadly one.
As far as we can tell, there aren’t any rogue planets hiding in the blind spots of our solar system, but there are plenty of rogue planets out there. They are almost impossible to detect and they don’t play by the rules which usually govern planets. Which is enough to make us wonder if von Trier knows something we don’t.
It’s just a planet, but it wears a leather jacket. Planets don’t necessarily have a whole lot in common with one another. Some of them are small and rocky and some are huge and gaseous. Some have moons or rings and others walk their orbital paths alone. Some have thin, wispy atmospheres and others are thick with clouds; still others are naked and barren. The one thing they all have in common is a cozy gravitational relationship with a star. Rogue planets dismiss that planetary requirement too.
A rogue planet’s defining characteristic is that it floats freely through space, untethered to any parent star. That horrifying fate, an entire world kicked out of the nest to wander the cosmos alone, might be way more common than we previously thought. Some rogues probably form independently, the result of a failed star, while others form inside protoplanetary disks around stars, just like the Earth. In the latter case, they are likely ejected from one of a number of intense gravitational events.
A planet might get separated from its family if another star or black hole passes too close to the system. That atypical gravitational nudge might be enough to ripple spacetime in just the right way and fling a planet out of its orbit. Something similar might happen without the influence of a passing star or black hole, during the early days of a stellar system, thanks to something called planetary migration.
When systems are still forming, planets begin coming together wherever the most matter happens to coalesce. As the star, planets, moons, and other cosmic objects grow and collect more mass, they command more of the gravitational landscape and begin to influence one another in new and changing ways. This leads to a chaotic early period during which the planets are in a state of flux. Planets that form in one part of the system can end up in an entirely different part of the system or get kicked out entirely.
Probably not, but it’s hard to say definitively. We know that rogue planets exist and we know that planetary collisions happen. Our own Moon is the product of one such collision between a proto-Earth and a fledgling planet called Theia. The probability of another planetary impact in the future isn’t zero, but it’s probably not worth worrying about.
We find rogue planets primarily through gravitational microlensing. When a rogue planet passes in front of a field of stars, its gravity warps the spacetime around it. Astronomers can tease out a detection from the way starlight bends around the planet as it travels through warped space. The small number of rogue planets we have discovered are far away and in no risk of ever coming anywhere near us. Everything else, the untold number of rogue worlds we haven’t found, that’s all probability.
Attempting to approach a number requires first having some idea of how many rogue worlds are out there and how likely they are to be in any one place (like the same place as the Earth) at any given time. The rough number of rogue planets in our galaxy, let alone the entire universe, is still unknown but one estimate puts it in the trillions. Rogue planets in the Milky Way (and probably in other galaxies, too) might outnumber stars 20 to 1.
They’re out there right now, like lone wolves stalking the dark forest of the cosmos, waiting to pounce. Fortunately for us, that dark forest is pretty dang big and the wolves are wandering aimlessly. Garrett Brown, a celestial mechanics and computational physics researcher at the University of Toronto, estimated the odds of a rogue planet entering the solar system at one in a billion over the next 1,000 years. He puts the odds of it getting as close as the orbit of Mars more like one in a trillion. Pretty long odds.
A separate doomsday possibility with slightly different origins but a similar outcome would be a collision with a planet from our own solar system. It’s possible, over time, that the orbits of one or more planets in the solar system will become unstable. Mercury or Venus might migrate further out or one of the outer planets might snuggle its way in. Regardless of the culprit, the ensuing gravitational chaos could be catastrophic to Earth life even if we didn’t get smacked directly. All of that is unlikely, too.
Our solar system has been stable for billions of years, since pretty shortly after its formation, and it probably will be for a long time yet. While there are limits to how far we can simulate orbits into the future, we’re confident that nothing weird is going to happen for at least tens of millions of years. If you want to hop on the back of another planet’s motorcycle and ride off into the sunset, you’re going to have to come up with another plan. There aren’t any rogue worlds headed our way for the foreseeable future.
But you can live out your doomsday fantasies in Melancholia, streaming now on Peacock.
In the film Melancholia, the physical planet Melancholia acts as a metaphor for depression. While Claire descends into debilitating panic and terror as the end nears, the depressed Justine surprisingly finds a sense of calm and clarity, feeling that the world itself is already corrupt and broken. I've seen the film and the visuals of the rogue planet Melancholia are stunning. The rogue planet is depicted as being significantly larger than Earth—estimated in dialogue and discussions to be roughly 10 to 20 times the size of Earth (with a diameter of at least 66,000 km, making it larger than Uranus). This is a scene from the film, at Justine’s disastrous wedding reception, the ultimate unwanted guest crashes the party, the rogue planet. You can see it lurking in the sky, the tiny blue object to the left.