Explanation:
The small constellation
Sagitta
sports this large piece of cosmic
jewelry, dubbed the Necklace Nebula.
The newly
discovered
example of a ring-shaped planetary nebula is
about 15,000 light-years distant.
Its bright ring with pearls of glowing gas is half
a light-year across.
Planetary nebulae
are created by sun-like stars in a
final
phase of stellar evolution.
But the Necklace Nebula's central star, near the center of a ring
strongly tilted to our line of sight, has also been shown to be
binary,
a close system of two stars with an orbital period
of just over a day.
Astronomers estimating the apparent
age of the ring to be
around 5,000 years, also find more distant gas clouds
perpendicular to the ring plane, seen here at the upper left and
lower right.
Those clouds were likely ejected about 5,000 years before the
clouds forming the necklace.
This false color image combines emission from
ionized hydrogen in
blue, oxygen in green, and nitrogen in red.
