What is a black hole?

Well, the name is actually a little misleading because black holes aren’t actually holes. They’re regions in space that have a gravitational pull that is so strong that nothing can escape, not even light. Scientists know about two different sizes of black holes — stellar-mass black holes and supermassive black holes.

A stellar-mass black hole is born when a massive star dies. That’s a star that’s larger than our own Sun. These stars burn up all the nuclear fuel in their cores, and this causes them to collapse under their own gravity. This collapse causes an explosion that we call a supernova. The entire mass of the star is collapsing down into a tiny point, and the area of the black hole is just a few kilometers across.

Supermassive black holes can have a mass of millions to tens of billions of stars. Scientists believe that every galaxy in the universe contains a supermassive black hole. That’s up to one trillion galaxies in the universe. But we don’t know how these supermassive black holes form. And this is an area of active research.

What we do know is that supermassive black holes are playing a really important part in the formation and evolution of galaxies, and into our understanding of our place in the universe.

[END VIDEO TRANSCRIPT]

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