Explanation:
NGC 2818 is a beautiful
planetary nebula,
the gaseous shroud of a
dying sun-like star.
It could well offer a glimpse of the future that
awaits our own Sun after spending another 5 billion years or
so steadily using up hydrogen at its core, and then finally helium, as
fuel for nuclear fusion.
Curiously,
NGC 2818 seems to lie within a sparse open star
cluster, NGC 2818A, that is some 10,000 light-years distant
toward the southern constellation
Pyxis
(Compass).
Since open star
clusters disperse after only a few hundred
million years, this one must be exceptionally old to
have one of its member stars evolve to the planetary
nebula stage.
At the distance of the star cluster, planetary nebula NGC 2818
would be about 4 light-years across.
The Hubble image
is a composite of exposures through narrow-band filters,
presenting emission from nitrogen, hydrogen, and oxygen atoms
in the nebula as red, green, and blue hues.
digg_url = 'http://apod.nasa.gov/apod/ap090122.html'; digg_skin = 'compact';
