A black hole is a place in space. Its gravity is so strong. Even light cannot get out. A black hole is a lot of matter. It is squeezed into a very small space. Black holes are invisible. That is because no light comes out of them. Black holes come in different sizes. The biggest are called supermassive black holes. Some have as much mass as millions of Suns.

Black holes do not roam around space eating stars and planets. From far away, a black hole pulls on things the same as any other object with the same mass. If the Sun turned into a black hole of the same mass, Earth would not be swallowed. Something can orbit a black hole safely if it stays far enough away. Only things that get too close fall in.

A stellar black hole forms when the center of a very big star collapses after the star runs out of fuel. Black holes grow bigger when they take in more stuff from around them. They can also get bigger by crashing into stars and other black holes. Black holes do not last forever. They very slowly shrink and evaporate.

The edge of a black hole is the event horizon. Nothing can come back out once it crosses it. The event horizon is not a hard surface like the ground. Gravity can be too strong to escape from. To leave Earth you need about 11 kilometers per second. Inside the event horizon you would need to go faster than light.

Gas that falls toward a black hole gets very hot. It glows. We can see the glow. We cannot see the black hole. Gas falling into supermassive black holes powers some of the most energetic things in the universe. That includes jets that launch particles to near light speed. Black holes can spin. Light and gas near them swirl around too.

Albert Einstein's ideas about gravity led scientists to predict that black holes can exist. In 2019, scientists showed the first picture of a black hole. It was in a galaxy called Messier 87. The picture shows a bright ring. In the middle is a dark spot.

Our Milky Way galaxy has a giant black hole at its center. In 2022, scientists showed the first picture of the black hole at the center of our galaxy. The black hole in the middle of the Milky Way is called Sagittarius A*. It has about 4 million times the mass of the Sun.

Words to know

• orbit: travel around
• supermassive: biggest black holes
• evaporate: shrink away

The short version

A black hole is a place in space where gravity is so strong that even light cannot get out. A black hole is a lot of matter squeezed into a very small space. Black holes are invisible, because no light comes out of them. Our Milky Way galaxy has a giant black hole at its center.

Quick facts

• Black holes come in different sizes.
• The edge of a black hole is called the event horizon.
• Nothing can come back out once it crosses the event horizon.
• Black holes grow bigger when they take in more stuff from around them.
• In 2019 scientists showed the first picture of a black hole.