Black Holes

At the center of our Milky Way is a huge black hole. It is called Sagittarius A* and has about four million times the mass of the Sun. It is around 27,000 light-years from Earth. It poses no danger to our solar system.

A black hole is a region in space where gravity is so strong that not even light can escape. Its boundary is called the event horizon. Anything that crosses this boundary cannot get back out. That is why we cannot observe what is inside.

Many black holes form when very massive stars run out of fuel. Their cores collapse under their own gravity. The remains of several stars do not first need to merge. Our Sun is not massive enough to form a black hole this way.

The centers of most large galaxies contain especially massive black holes. How they originally formed is not yet fully understood. Some may have formed through the direct collapse of enormous gas clouds in the early universe. They can grow by absorbing matter or merging with other black holes.

Although black holes do not emit light themselves, researchers can observe their effects. Nearby stars move under their influence. Gas can collect in a disk around a black hole, heat up intensely, and glow brightly.

Black holes do not suck in everything around them. Stars can orbit them on stable paths. Matter can fall in only when it gets too close.

Study sentences

At the center of our Milky Way is a huge __________.
This black hole is called __________.
It has approximately the mass of four million __________.
It is about __________ light-years from Earth.
The gravitational pull of a black hole is so strong that not even __________ can escape.
The boundary of a black hole is called __________.
Many black holes form when very massive __________ have used up their fuel.
Our Sun is too __________ to form a black hole.
Gas can collect in a __________ around a black hole and glow brightly.
Stars can orbit black holes on stable __________.