Written for the KidsKnowIt Network by:
Gemma Lavender, MPhys, FRAS
A binary (two) supermassive black hole system. Image captured by NASA's Chandra X-ray satellite.
Have you ever heard of a black hole? You might well have done. But we are not talking about a hole in the ground, we are talking about the ones that astronomers believe exist in our gigantic Universe. Despite their name, scientists believe that there is a lot more to these objects. So what exactly is a black hole?
If you were to ask an astronomer this question, they are most likely to say that a black hole must be one of the most strangest objects ever. They are almost like an incredibly strong vacuum cleaner without the noise - not only would the crumbs from under your bed be unable to escape, but anything that happens to travel past would have a hard job trying to wriggle free from its clutches, too. Do you know what causes a black hole to gobble up everything in sight? Have a go at guessing what the answer might be before you carry on reading. Perhaps you can get into a group with your friends and think of some answers - drawing pictures of a black hole might be able to help you to figure it out!
If you have not already figured it out, the answer to the question is gravity - the force that does not only keep the planets in orbit around the Sun, but keeps our feet on the ground. You might think that the earth would have to have some pretty strong gravity to allow us to walk and run on its surface, but a black hole is even stronger - even light has a pretty tough time of pulling away and that is the fastest thing that we know of, racing at a speed of 186,000 miles per second. For that reason, black holes are probably the darkest things that you will ever find!
Just where this strong gravity comes from is certainly not in the name. You might be amazed to learn that these objects are not empty; they are filled with lots and lots of material that is crammed into a very small space - just imagine stuffing your house (and everything that is in it) into a thimble! Because there is so much material in one place, this is what causes the strong gravity. Now, isn’t that cool?