Black holes are points in space that are extraordinarily dense. They apparently arise when the mass of a large star becomes compressed into a point smaller than an electron (we're not making this up!). In those conditions, the gravity becomes so enormous that not even light can escape.
The black hole -- located at the bottom of the "funnel" -- warps the fabric of space and time, shown by the lines. If you shine a laser toward the hole, its light would curve along these lines. A jet of particles leaves the region near the black hole at almost the speed of light. The glowing stuff is matter being sucked into the hole. Courtesy Sky and Telescope magazine, Joe Bergeron, artist.
Ironically enough, although the prediction for black holes was based on Einstein's theories, he himself argued against their existence in a rare instance of public blundering (see "The Reluctant Father of Black Holes" in the bibliography).
At any rate, scientists now think black holes form after an old star explodes as a supernova. The remaining junk can no longer withstand its own gravity, so it collapses in on itself and forms a strange celestial item.
Small stars proceed to become neutron stars, extremely dense items about the size of a Manhattan that retain most of the mass of the original star. Unlike black holes, neutron stars are not dense enough to restrain light.
Larger original stars become black holes -- the weirdest of the weird.
Not my problem...
So the only way to detect a black hole is by looking for junk getting sucked into an invisible point in the sky. As it hastens to oblivion, this doomed matter emits characteristic X-rays, which give clues about the weird effects of the black hole's stunning gravitational prowess.
Earlier this year, Wei Cui and his colleagues at the Massachusetts Institute of Technology measured the rotation of a black hole at several thousand revolutions per second. Then, on Nov. 6, his group reported that the spinning gravity of several black holes distorted spacetime, giving it the shape of a funnel. On the same day, a similar study of neutron stars was published by Italian researchers Luigi Stella and Mario Vietri.
Can't put it off any longer.
It's not something you're likely to confront any time soon, but if you got close to a black hole, you'd get sucked in. If you survived (you wouldn't) you'd have quite a tale to tell -- except nobody would hear it, since nothing leaves a black hole, not even stuff as lightweight as light or radio waves.
Time for our six-minute guide to space-time.
