What is a Black Hole? We Asked a NASA Expert

Nasa Space

What exactly is a black hole? Well, they’re not holes at all, rather incredibly dense regions in space with gravity so strong, not even light can escape.   There are stellar-mass black holes, which form when massive stars collapse and explode in a supernova, and supermassive black holes, which are millions to billions of times more massive and sit at the centers of galaxies.   Scientists know these cosmic powerhouses shape galaxies and influence how the universe evolves. But how do supermassive black holes form? That’s still one of astronomy’s biggest mysteries. A NASA scientist explains what we know (and don’t know) about these cosmic gargantuans.

Transcript

00:00What is a black hole? Well, the name is actually a little misleading because black holes aren't

00:11actually holes. They're regions in space that have a gravitational pull that is so strong that

00:17nothing can escape, not even light. Scientists know about two different sizes of black holes,

00:24stellar mass black holes and supermassive black holes. A stellar mass black hole is born when a

00:29massive star dies. That's a star that's larger than our own sun. These stars burn up all the nuclear

00:35fuel in their cores and this causes them to collapse under their own gravity. This collapse causes an

00:43explosion that we call a supernova. The entire mass of the star is collapsing down into a tiny point

00:49and the area of the black hole is just a few kilometers across. Supermassive black holes can

00:56have a mass of millions to tens of billions of stars. Scientists believe that every galaxy in the

01:03universe contains a supermassive black hole. That's up to one trillion galaxies in the universe. But we

01:10don't know how these supermassive black holes form and this is an area of active research. What we do

01:16know is that supermassive black holes are playing a really important part in the formation and evolution

01:22of galaxies and into our understanding of our place in the universe.

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