Image Credit & Copyright: Adam Block, Mt. Lemmon SkyCenter, University of Arizona
Explanation: Ghostly in appearance,
Abell 39 is a remarkably simple, spherical nebula about five light-years across. Well within our own
Milky Way galaxy, the cosmic
sphere is roughly 7,000 light-years distant toward the constellation Hercules.
Abell 39 is a
planetary nebula, formed as a once sun-like star's outer atmosphere was expelled over a period of thousands of years. Still visible, the nebula's central star is evolving into a hot
white dwarf. Although faint, the nebula's simple
geometry has proven to be
a boon to
astronomers exploring the chemical abundances and
life cycles of stars. In
this deep image recorded under dark night skies, very distant
background galaxies can be found -- some visible right through the nebula itself.
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