The last gasp of a dying star produces a spectacular cloud of gas and dust in this Hubble Space Telescope image. When first seen through a telescope more than two centuries ago, its outline resembled that of the planet Saturn, so it was named the Saturn Nebula. (It is also known by the catalog number NGC 7009.) It is about 1,400 light-years away, in Aquarius. As a star like the Sun nears the end of its life, it expels its outer layers into space, forming a colorful shell of gas and dust like this one. The Sun will undergo this fate in several billion years. [Bruce Balick et al./NASA]
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Saturn is just climbing into good view in the early morning sky right now. The planet’s low in the east at first light, and looks like a fairly bright star. The true star Spica is a little to its right.
An object that looks a lot like Saturn is in the early evening sky: the Saturn Nebula. It’s well up in the south at nightfall, at the western edge of Aquarius.
Through a telescope, its outline looks like Saturn seen with its rings nearly edge-on. Unlike golden Saturn, though, the nebula shines blue or green. That’s because the Saturn Nebula is nothing like its namesake. Instead, it’s a final blaze of glory for a dying star.
Originally, the star was similar to the Sun. For billions of years, it steadily burned the hydrogen fuel in its core. When that supply was used up, though, the star began to change.
First, it expelled its outer layers, forming an expanding shell. It then began to burn the hydrogen in a thin layer around the core. That heated the star’s surface to a hundred thousand degrees Fahrenheit. At that temperature, the star pumps out lots of ultraviolet energy, causing the shell around it to glow. Radiation and particles from the star have also carved a “bubble” in the center of the shell.
That’s created a complicated structure — shells within shells, and high-speed “jets” squirting away from them. This beautiful nebula will last for millennia — until the gas dissipates into the galaxy, leaving behind only the star’s dead core.
Script by Damond Benningfield, Copyright 2011
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