Black holes are strange things in Space that scientists are still trying to understand. They were first thought of by Albert Einstein, a very famous scientist who did lots of thinking about maths and physics. Einstein’s ideas about how Space and time worked made him think that there might be ‘black holes’ in Space. But black holes weren’t actually discovered to be real until 55 years after Einstein first had the idea of them!
So what are they? Well, black holes are sort of made from old stars. So, we should start by thinking about what stars are made of, then figure out how they can turn into black holes. And then we can figure out why they are called black holes and whether they are actually black!
You might remember from one of my earlier posts that stars are bright, shining balls of gas in Space. They are mostly made up of two chemical elements (hydrogen and helium) which are taking part in a huge reaction that gives out lots and lots of light and heat.
When a star runs out of hydrogen, the chemical reaction stops and the star collapses. If this happens, all the stuff that was inside the star gets squashed into a very small space. When lots and lots of stuff is packed into a tiny space, it creates a strong force (called ‘gravitational force’) which pulls towards it any dust and gas in the Space around it.
If a big star collapses, the densely-packed space where the star used to be can become a ‘black hole‘. Black holes are super-dense and make a super-strong gravitational force, which pulls in dust and gas from Space, allowing them to grow to enormous sizes.
We use the word ‘black’ to describe what we can see when there is no light around. We can’t see black holes in Space and that’s the reason they got their name – it’s not that they are black, it’s that we can’t actually see them.
So how do we know they are there at all? Well, even though black holes don’t give out light, they can pull light in. So, scientists are able to find black holes in Space by looking for streaks of light being drawn towards them.
If you want to find out more about these weird and wonderful black holes, check out this website for some amazing facts.