The Beautiful Dying Star
"Garden-variety stars like our Sun live undistinguished lives in their galactic neighborhoods, churning out heat and light for billions of years. When these stars reach retirement age, however, they become unique and colorful works of art. As ordinary, sun-like stars begin their 30,000-year journey into their twilight years, they swell and glow, shrugging off their gaseous layers until only their small, hot cores remain.
The ejected gaseous layers are called planetary nebulae, so named in the 18th century because, through small telescopes, these gas clouds had round shapes similar to distant planets such as Uranus or Neptune.
The gaseous debris glows like a fluorescent design, producing objects with striking shapes and names like "The Ring Nebula" and "The Spirograph Nebula." Astronomers have recorded more than 1,000 of them in our galaxy."
From "The Glorious End Of Stellar Life", STScI Astrofile
Raghvendra Sahai and John Trauger's (JPL) Planetary Nebulae Gallery
Arsen Hajian and Yervant Terzian's (USNO) Planetary Nebulae Gallery
Bruce Balicks's (U. Washington) Planetary Nebulae Gallery
Robin Ciardullo's (Penn State) Planetary Nebulae Gallery