A black hole steals gas from a giant companion star in this artist's concept of Cygnus X-1 , one of the first black holes discovered. The hot gas forms a superhot disk around the black hole. The disk emits enormous amounts of X-rays (inset, X-ray image from Chandra X-Ray Observatory). A recent study found that Cygnus X-1  is about 6,000 light-years away. The black hole is 15 times the mass of the Sun, and it spins about 800 times per second. [ESA/Hubble; inset: NASA/CXC]
Six million years ago, a brilliant star suddenly vanished from view. The star could no longer produce energy in its core to counteract the inward pull of gravity, so in a matter of hours, it collapsed. Its great mass was crushed to an infinitely small point, then hidden from the outside universe — behind the event horizon of a black hole.
Although it produces no energy at all, this black hole is one of the most intensely studied objects in the galaxy. It’s known as Cygnus X-1 — the first source of X-rays discovered in the constellation Cygnus.
The X-rays come not from the black hole, but from gas that’s stripped from a brilliant companion star. As the gas spirals toward the black hole, it’s heated to hundreds of millions of degrees, so it produces copious amounts of X-rays.
Astronomers have been studying the system for 40 years. But it wasn’t until just last year that they finally nailed down the details.
They measured the distance to Cygnus X-1 at 6,000 light-years. That allowed them to accurately measure the mass of the black hole — 15 times as massive as the Sun. And they also measured how fast the black hole is spinning — about 800 times per second.
Those numbers helped astronomers calculate when the black hole was born, which indicated how it was born. The original star probably didn’t explode as a supernova, which is the birth process for many black holes. Instead, it simply collapsed — giving birth to a black hole.
Script by Damond Benningfield, Copyright 2012
For more skywatching tips, astronomy news, and much more, read StarDate magazine.