Shapley 1: An Annular Planetary Nebula
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This strange structure is what can result when a normal
star
runs out of
nuclear fuel
in its core. At that time, the center condenses into a
white dwarf while the outer atmospheric layers are
expelled into space and appear as a
planetary nebula.
This particular
planetary nebula, designated Shapley 1 after
the famous astronomer
Harlow Shapley, has a very apparent annular ring like
structure. Although some of these nebula appear like planets on the sky
(hence their name), they actually surround stars far outside our solar system.