What exactly is a black hole?

We’ve heard the term a lot, but very few of us understand it — what in the heck is a black hole?

According to NASA, a black hole is not empty space, contrary to popular belief. In fact, it generally forms from the remains of a large star that has exploded into a supernova and consists of a large amount of matter that is packed into a very tight area. Its gravitational pull is so strong that light can’t even escape it.

A black hole also defies the laws of physics: It distorts the space-time continuum. At its edge is the event horizon, where time passes slower than time on Earth, Britannica explains. The deeper a person ventures into the black hole, the more distorted time becomes.

Researchers have yet to directly see a black hole for themselves but have been able to deduce where one is by the activity of matter nearby, NASA notes. If the black hole passes through interstellar matter, that matter will be sucked in through a process called accretion. If, however, a star passes by a black hole, that star will be pulled in and torn apart. The attracted matter around the hole will then heat up and emit x-rays that scientists can observe via telescopes.

NASA points out the most recent black-hole discovery took place on February 27, when a giant black hole in the center of the Ophiuchus galaxy cluster caused the biggest explosion in the universe. The cluster is located approximately 390 million light years on Earth.

To find out more, check out the above episode of “Space Down to Earth.”If you enjoyed this story, you might want to check out the best photos of Earth taken from space.

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