WHAT IS A BLACKHOLE ?

A black hole is a place in space where gravity is so strong that no particles or even electromagnetic radiation such as light can escape from it. 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.

HOW BIG ARE BLACKHOLE ?

Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain. Mass is the amount of matter, or "stuff," in an object.

Another kind of black hole is called "stellar." Its mass can be up to 20 times more than the mass of the sun. There may be many, many stellar mass black holes in Earth's galaxy. Earth's galaxy is called the Milky Way. Stellar-mass black holes are typically in the range of 10 to 100 solar masses, while the supermassive black holes at the centers of galaxies can be millions or billions of solar masses. The supermassive black hole at the center of the Milky Way, Sagittarius A*, is 4.3 million solar masses.

The largest black holes are called "supermassive." These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center. The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns and would fit inside a very large ball that could hold a few million Earths.

HOW BLACKHOLES WERE BORN ?

A star's life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Its total mass is the main factor determining its evolution and eventual fate. A star shines for most of its active life due to the thermonuclear fusion of hydrogen into helium in its core. This process releases energy that traverses the star's interior and radiates into outer space. At the end of a star's lifetime, its core becomes a stellar remnant: a white dwarf, a neutron star, or—if it is sufficiently massive—a black hole.

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

HOW BLACKHOLES DIES ?

Inside what's known as the black hole's event horizon, not even light itself can escape from a black hole. But that doesn't mean that black holes will live forever; on the contrary, they slowly decay away due to a phenomenon known as Hawking radiation.

This energy takes the form of a slow-but-steady stream of radiation and particles that came to be known as Hawking radiation. With every bit of energy that escapes, the black hole loses mass and thereby shrinks, eventually popping out of existence altogether.