The image above is of "The Eskimo Nebula" or, "The Clown Face Nebula", whichever you prefer. i think it looks more like an Eskimo with his fluffy hood around his face.
This Planetary Nebula is the fate that awaits our Sun in around 4.5 billion years.
Despite its name, a Planetary Nebula has nothing to do with planets. Their name was coined by astronomers who first peered through their small telescopes at them, believing them to resemble planets because of their disc-like appearance.
As mentioned above, this is the fate that awaits our Sun, stars bigger than our Sun will either die in a spectacular fashion in a supernova explosion or in a black hole. (See "Supernovae" and "Black Holes" topic pages.)
When a star's central hydrogen has all been converted into helium, the core is pulled inwards, squeezing it hotter until the helium atoms collide faster in order to overcome the fiercer electric repulsion, and this demands a higher temperature.
When the helium itself is used up, the star contracts and heats up even more, and produces carbon. This process only continues as far as carbon, because the temperature of a star who's mass is between 0.1 and 1.4 times that of the Sun does not increase sufficiently to trigger off carbon-burning.
As this size of star's hydrogen fuel begins to run low, it expands and becomes unstable, and the outer layers swell out, cooling as they do so. The star becomes a red giant.
The red giant phase lasts for around 10,000 years, afterwhich the star's outer layers are thrown off, and for around 100,000 years or so we have what is known as a planetary nebula.
When the final layers have dissipated, what is left is a white dwarf star. A white dwarf's core is so amazingly dense that if just a spoonful of it was brought to Earth, it would weigh more than an elephant!
A white dwarf continues to shine weakly for an extremely long period before losing the last of its heat and becoming a cold, dead black dwarf.
