September 4, 2012
Late Night Heavy Lifting
The Dumbell Nebula. M27. First noted by Charles Messier in 1764, this spectacular planetary nebula lies about 1200 light years away. Contrary to its name, a planetary nebula has nothing to do with planets. They were named that for their disc like appearance in early telescopes, much like planets.
What we now know them to be is a shell of gas ejected by a star as it begins to collapse at the end of its life. The outer layers of the star are thrown off and expand out into space. This particular nebula is expanding at about 17 miles per second. In another few thousand years the gas will expand to the point that it is too diffuse to see and the white dwarf at its center will be all that remains.
In this nebula you can see the bright white dwarf right at the center of the nebula. It is that star which lights up the hot gasses. The different colors come from the different gasses. Red is hydrogen gas and the blue green is mostly oxygen.