Cygnus, the swan, is beginning its annual nosedive toward the western horizon. It's high overhead at nightfall, but drops down the western sky later on. As it does so, it looks less like a swan and more like its other namesake, a cross.
Cygnus is home to one of the most interesting star systems in the galaxy: Cygnus X-1. It's a binary system that appears to consist of a bright blue supergiant star and a black hole.
A black hole is an object with such powerful gravity that nothing can escape from it, including light. This black hole formed when the core of a supergiant star collapsed, perhaps blasting the star's outer layers into space as a bright supernova.
The black hole is stealing gas from the companion star. The gas forms a hot, bright disk around the black hole. Some of the material actually evades the black hole, and shoots back into space in the form of two high-speed "jets." They're like geysers of electrically charged particles. A strong magnetic field funnels the jets into space.
A few years ago, astronomers found that the jets have carved a giant bubble in the gas around the black hole. The bubble spans about 10 light-years, and it appears to be expanding at more than 200,000 miles an hour. From that speed and size, astronomers estimate that the bubble has been growing for about a million years. So that means that the black hole in Cygnus X-1 must be at least a million years old.
Script by Damond Benningfield, Copyright 2005, 2008
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