It is hard to fight the gravity of small objects that are packed tightly together. The gravity of a neutron star is almost impossible for an object to escape. Only fast-moving gas and electromagnetic radiation, such as light, heat and radio waves, can succeed. And if a star could be made even more compact, nothing could leave its surface. Not even light.

If everything fell in and nothing came out, this would be similar to a hole in space. Since even light cannot escape, astronomers call such an object a black hole. When a large star explodes, it leaves behind an inner core that can become a neutron star. But if the core contains more than three times the mass of our sun, it can be squeezed into a black hole.

If even light cannot escape a black hole, how can scientists find them? The only way to identify a black hole is through its interactions with other matter atronomers can see. If the black hole orbits a star, for example, some of the star’s gas may flow into the black hole. As gas falls toward the hole, it swirls into a flattened disk. Its molecules move even faster, bunching up and colliding. This makes the gas very hot - so hot that it gives off x-rays. Although we can’t see the black hole, satellites can detect the x-rays. The first black hole to be confirmed was found in the core of the giant galaxy M87 in 1994. In addition, a good candidate for a black hole is an x-ray source that circles an orange star in the constellation Monoceros. Another possible black hole orbits a giant blue star in the constellation Cygnus.

Black holes are an interesting part of our solar system.

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