The Dumbbell Nebula (M27)

The Dumbbell Nebula in the constellation Vulpecula (the fox) is an example of a "planetary nebula." These are formed when a star comparable to our sun exhausts its hydrogen fusion process and blows off its outter layer into space. The glowing gas is a thick ring around the equator of the star, which we from our vantage point is viewed nearly edge on. The nebula is about 1200 light years away and is 2 light years in diameter. The red glow is from ionized hydrogen and the blue-green from ionized oxygen.

The remnant central star, visible in the photo, is a white dwarf. It is composed of hot dense matter, but lacks a fusion engine at its core. The stellar explosion happened about 1000 years ago and the glowing gas continues to expand outward. A similar fate awaits our sun in 5-8 billion years. White dwarfs slowly radiate their heat away and will eventually become cold black dwarfs. The universe is not yet old enough for any black dwarfs to have appeared.