planetary nebula, the gaseous shroud of a dying sun-like star. It could well offer a glimpse of the future that awaits our own Sun after spending another 5 billion years or so steadily using up hydrogen at its core, and then finally helium, as fuel for nuclear fusion. Curiously, NGC 2818 seems to lie within a sparse open star cluster, NGC 2818A, that is some 10,000 light-years distant toward the southern constellation Pyxis (Compass). Since open star clusters disperse after only a few hundred million years, this one must be exceptionally old to have one of its member stars evolve to the planetary nebula stage. At the distance of the star cluster, planetary nebula NGC 2818 would be about 4 light-years across. The Hubble image is a composite of exposures through narrow-band filters, presenting emission from nitrogen, hydrogen, and oxygen atoms in the nebula as red, green, and blue hues.
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Publications with keywords: planetary nebula - open cluster
Publications with words: planetary nebula - open cluster