With Christopher Nolan’s newest film Interstellar, now in cinemas (see our recent article on the incredible black hole at the heart of this film) it’s safe to say that black holes are becoming quite the subject of choice in science. The question of what would happen if one were in close proximity to Earth is still pondered, and is a petrifying yet fascinating thought.
Firstly, what exactly is a black hole? It’s a region in space where the gravity is so strong that not even light can escape. Since no light escapes we can only see the effects they have on their surroundings. Black holes vary in size, the smallest ones are about the mass of a mountain whereas a regular black hole is about 20 times the mass of the Sun, but they can get even larger. These devastating phenomena are generally formed when a star reaches the end of its life and collapses inwards on itself.
Low mass black holes are known as primordial black holes and are a predicted by-product of the big bang along with creation of the universe. However they aren’t expected to live very long as black holes are theorised to radiate energy and lose mass, but some may still survive to this day.
The largest supernovae create supermassive black holes and are roughly a million times the mass of the Sun. These supermassive black holes are found at the centre of galaxies.
If a black hole entered our solar system what would happen? Even with the smallest black holes, with the mass of a mountain it would still be catastrophic, surely? Fortunately not, but let’s explore it anyway even though it is disappointing (to me at least). From theory, we expect a primordial black hole to pass through matter but we would still be able to see its side effects. Energy roughly equal to that of a tonne of TNT will be emitted in the form of particles and antiparticles. This would be the total energy passing through all of the Earth – we wouldn’t even feel a tremor.
With a ‘regular’ black hole it’s much more exciting. At the furthest reaches of the solar system the black hole would pass through the Oort cloud and send comets and meteors flying throughout the solar system.
Unnervingly, the black hole would be invisible besides the small amount of light bent from distant stars until it begins to tear material from the gas giants such as Neptune and Uranus. It would then have a disk of super heated dust and gas surrounding it. If any planet were directly in its path it would be completely consumed. Finally as the black hole nears Earth it will cause earthquakes and super-volcanoes until it finally reaches our orbit, and we’re left with a lava filled planet.
But what about a supermassive black hole? Within a thousand light years the solar system’s orbit around the galaxy would be disrupted without directly affecting planet Earth. At a few hundred astronomical units (the distance between the Earth and the Sun) the orbits of the planets would be affected. The Earth could either be flung into space and freeze, forced closer to the Sun and boil, or consumed by the Sun itself. We could even end up in a large orbit around the black hole or get thrown into it.
In the worst scenario if the black hole was one astronomical unit away the Earth would simply be torn apart by gravitational forces. We don’t need to worry about this though, they are extremely rare and far away from Earth.