A black hole is black because it absorbs all wavelengths of light, which makes a black hole virtually invisible. We can’t see black holes, but we can detect them by the effect they have on objects around them. For instance, black holes can be detected by X-ray telescopes.

Black holes are like stars in that they are in fixed orbits. They don’t ‘roam around’

The speed of light is 300 000 km/s, which is the speed limit of the Universe. Even at this speed, light is not fast enough to escape the enormous force of gravity of black holes.

This is extremely unlikely

Black holes are formed by the complete gravitational collapse of massive stars with core masses of at least eight times the mass of the Sun.

Check the diagram showing the life cycle of stars included in this kit. Red supergiants have enough mass to eventually become black holes.

Yes, it is possible for an object to cross the event horizon and survive, if the black hole is weak. If the black hole is weak, its gravitational gradient is weak and it is this gradient that pulls objects apart after they cross the event horizon. However, nothing can survive all the way to the centre (the ‘singularity’). It would inevitably be destroyed and become part of the mass of the black hole.

There would be no reason why two black holes could not collide. This is a major area of research involving very complicated computations. The research aims to define what sort of gravitational wave output two colliding black holes would create, so that this could be searched for and detected.

Our Sun is not massive enough to become a black hole. A star needs to be at least eight times the mass of the Sun to form a black hole.

For a long-time astronomers thought that black holes could only grow, as they swallow up matter in their path. The work of Stephen Hawking and others has shown, however, that black holes can radiate energy and lose mass (by quantum processes). It would, however, take longer than the lifetime of the universe for a stellar black hole to evaporate.