Science fiction leads us to believe black holes are tunnels in space. A person sucked into a black hole's gravity well would be spit back out somewhere else in space. Although this is an intriguing idea, it could never be true. If you fell into a black hole, you'd never survive to tell your tale. As you progressed down the gravity well of the black hole, the gravity on your feet would pull much harder than the gravity on your head. Your body would stretch...and stretch...and stretch.
Eventually, the atoms in your body would begin to separate and grow farther apart until the matter that composed you were ripped apart to become part of the black hole itself.
Maybe that's not the best form of space travel!
Science fiction aside, a black hole is actually the crushed core of an exploded star. It is a perfectly round sphere of unimaginable smoothness. A black hole is so massive and yet so compact, nothing can escape its gravitational pull -- not even light.
The Hubble Space Telescope discovered a black hole in the center of galaxy M87. It has the mass of three billion suns, yet it is concentrated into a space no larger than our solar system. The velocity of the gas inside the galaxy's core is so high, only the tremendous gravitational field of a black hole could cause the gas to spin so fast.Hubble Measures the Speed of Gas in a Black Hole
Some spectral lines of elements in the light on one side of the swirling disk are blueshifted -- spinning toward the Earth -- while the other side of the disk is redshifted -- moving away from the Earth. Both sides are moving at the same velocity -- 1.2 million miles per hour. Could these speeds indicate anything other than a black hole? The high velocity could be caused by millions and millions of stars, but there are not enough stars in that area to create such a powerful attraction.
Black holes were mathematically predicted as early as 1926. In the late 1960s x-ray sources in space and other indirect evidence suggested the presence of black holes. In 1994, Hubble confirmed their existence.