What is a Black Hole ?

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.

Because no light can get out, people can't see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.

A black hole can not be seen because strong gravity pulls all of the light into the middle of the black hole. But scientists can see how the strong gravity affects the stars and gas around the black hole. Scientists can study stars to find out if they are flying around, or orbiting, a black hole.

When a black hole and a star are close together, high-energy light is made. This kind of light can not be seen with human eyes. Scientists use satellites and telescopes in space to see the high-energy light.

Scientists think the smallest black holes formed when the universe began.

Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.

Scientists think supermassive black holes were made at the same time as the galaxy they are in.

YouTube Link - https://www.youtube.com/watch?v=e-P5IFTqB98

Credits - https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-a-black-hole-k4.html

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What is Reflection of Light ?

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What is Universe ?

The universe is all the matter, energy, and space that exist. We can observe only a part of it - the observable universe. The entire, universe, including the part we cannot see, may be infinite. Galaxies form and evolve within an expanding and cooling universe. Because light takes billions of years to cross the cosmos, we see distant galaxies as they were at earlier times. Astronomers not only theorize about cosmic evolution - they can actually observe its various stages. The Big Bang is the scientific description of the origin of the cosmos. It describes the beginning of the universe as an explosion of space, which has expanded and cooled ever since. If we rewind the expansion of space and go backward in time, galaxies crowd closer and closer together in the past. Ultimately, all matter and energy is compressed at extremely high density and temperature. The observable universe fits within a volume smaller than a grain of sand. That superdense medium exploded in the Big Bang, l

SCIENCE IN UNIVERSE

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