Black holes are regions of space where gravity is so extreme that nothing, not even light—the fastest thing in the universe—can escape.
But is there a possibility that planet Earth will ever be pulled into a black hole? And if so, what would happen in this scenario?
What are the chances of Earth being consumed by a black hole?
Experts who spoke to Newsweek said there is practically zero chance of the Earth ever colliding with a black hole before it is swallowed by the sun in around five billion years’ time.
“For starters, space is aptly named,” Doug Gobielle, a professor in the physics department at the University of Rhode Island, told Newsweek. “The overall average luminous matter density of the universe is about one proton [a particle of light] per cubic meter. In the galaxy and the solar system this density is significantly higher, but still almost non-existent.”
“Objects we might deem as ‘large’ and ‘dense’ are fairly rare in the grand scheme of the universe, these being planets, stars, and the associated stellar remnants stars leave behind including white dwarfs, neutron stars and black holes,” Gobielle said.
While there are countless stars in our galaxy alone, random encounters between them are extremely rare due to the immense space between the objects, Jonathan Zrake, an assistant professor of physics and astronomy at Clemson University, told Newsweek.
“Short of a hyper-advanced civilization with near-unlimited resources and energy that would purposefully ‘launch’ a black hole towards the solar system, such an encounter is so unlikely as to be close to zero,” Gobielle said.
“In the same way as we do not generally worry ourselves about stars passing through the solar system, this can be extended to all objects in the galaxy,” he said.
“Stars do wander close enough, from time to time, to dislodge a few comets from the farthest outer regions of the solar system, called the Oort Cloud, but this is the extent of their gravitational impact on the solar system and it would likely be the same case for any black holes or other compact masses which would wander, by happenstance, past the solar system.”
Do any ‘nearby’ black holes pose a threat?
The closest black holes to our solar system are far too distant to have any kind of effect on our solar system, according to experts.
For example, V616 Monocerotis (V616 Mon), thought to be among the closest black holes to our solar system, is located more than 3,000 light-years away.
“Even if the black hole consumed its binary partner, there just isn’t enough mass to do anything exceptional except produce some outbursts of radiation,” Gobielle said. “At its distance from Earth, we would only notice this by looking directly at the system with powerful observational tools. The impact on Earth would be zero.”
Black holes come in two main size classes: stellar and supermassive (although recent research has revealed that there is likely also an intermediate class). Stellar black holes tend to have masses several times greater than our sun. Supermassive black holes, on the other hand, can have masses ranging from millions to billions of solar masses.
Stellar-mass black holes, like V616 Mon, form as the remnants of massive stars that die in cataclysmic cosmic explosions known as supernovae. One nearby star that could form a black hole in principle is Betelgeuse, the second brightest star in the constellation Orion.
According to Zrake, Betelgeuse is nearing the end of its life and will likely produce a supernova sometime in the next 10,000 years or so. But this star lies around 500 light-years away and if it does produce a black hole, there would be no impact on Earth.
How close would we have to get to a black hole for it to have an impact?
While it would be challenging to miss a supermassive black hole, or even an intermediate-mass black hole anywhere near the solar system, a stellar-mass black hole wandering close to the solar system without us readily noticing early on is within the realm of possibility, Gobielle said.
“[But] even a large stellar-mass black hole, say 30 solar masses, would have to be closer than Neptune (roughly 30 times the Earth-sun distance) to begin to have gravitational impacts on Earth, and about the distance of Jupiter (roughly five times the Earth-sun distance) to pull on Earth with roughly equal gravitational force to sun’s gravitational hold on Earth,” he said.
Black holes have a reputation for being omnipotent cosmic vacuum cleaners that consume everything in their path, but the reality is somewhat different, according to Gobielle.
“Black holes, generally speaking, are awful at consuming matter,” he said. “The general litmus test for this is to consider why the universe has not been consumed by black holes, the answer to which is that black holes are highly inefficient, under most circumstances, at consuming matter and growing to larger sizes.”
What If Earth Were Sucked Into a Black Hole?
If a black hole somehow came extremely close to Earth (closer than the moon’s orbit, for example) and was traveling slowly enough then our planet would likely be ripped apart by the extreme gravitational forces of the object.
“The atmosphere and oceans would be stripped from the Earth’s surface, and molten metal would pour from the earth’s mantle into space,” Zrake said.
This terrestrial debris would go into orbit around the black hole, and get vaporized into ionized gas—i.e. a gas consisting of atoms or molecules that have lost or gained electrons. The gas would form a ring of material around the black hole, known as an accretion disk, and most of it would be consumed over the course of a few hours to days, according to Zrake.
“Energy released from the plunging gas would drive powerful winds of plasma [one of the four fundamental states of matter consisting of charged particles] into space, and produce high-energy radiation. That light could probably be detected as a brief flash of hard X-rays by nearby extra-terrestrial astronomers,” he said.
But the chances of this scenario occurring are astronomically low. Slightly more plausible, but still incredibly unlikely, is a scenario where a black hole came sufficiently close to have an impact on the Earth, although not close enough to consume our planet.
The main danger here, for life at least, would be the black hole perturbing Earth’s orbit enough to affect the climate, or potentially dislodging enormous amounts of debris in the solar system (such as asteroids, comets and moons) and placing it on a collision course with our planet, according to Zrake.
“While life on Earth could likely survive such an event, humanity and almost all multicellular species on Earth almost assuredly would not,” Gobielle said.