An object known to amateur astronomers as the Little Ghost Nebula has been photographed by the Hubble Space Telescope, revealing details of the fuzzy object not visible from the ground.
The nebula, officially called NGC 6369, appears in most telescopes as a small, ghostly cloud surrounding a faint, dying central star. It resides the constellation Ophiuchus, between 2,000 and 5,000 light-years away.
Heres how Hubble astronomers think the colorful structure was created:
When a star with a mass similar to that of our own Sun nears the end of its lifetime, it expands in size to become a red giant. The red-giant stage ends when the star expels its outer layers into space, producing a faintly glowing nebula. Astronomers call such an object a planetary nebula, because its round shape resembles that of a planet when viewed with a small telescope.
The Hubble photograph of NGC 6369, captured with the Wide Field Planetary Camera 2 in February and released today, shows details of the ejection process.
The remnant stellar core in the center is now sending out a flood of ultraviolet (UV) light into the surrounding gas. The prominent blue-green ring, nearly a light-year in diameter, marks the location where the energetic UV light has stripped electrons off of atoms in the gas. This process is called ionization.
In the redder gas at larger distances from the star, where the UV light is less intense, the ionization process is less advanced. Even farther outside the main body of the nebula, one can see fainter wisps of gas that were lost from the star at the beginning of the ejection process.
The color image has been produced by combining pictures taken through filters that isolate light emitted by three different chemical elements with different degrees of ionization. The doughnut-shaped blue-green ring represents light from ionized oxygen atoms that have lost two electrons (blue) and from hydrogen atoms that have lost their single electrons (green). Red marks emission from nitrogen atoms that have lost only one electron.
Our own Sun, considered middle-aged right now, may eject a similar nebula, but not for another 5 billion years or so. The gas will expand away from the star at about 15 miles per second, dissipating into interstellar space after some 10,000 years. After that, the remnant stellar ember in the center will gradually cool off for billions of years as a tiny white dwarf star, and eventually wink out.
Scientists arent sure what will happen to Earth during all this, but the
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