Sharpless
308: Star Bubble
From
NASA’s Astronomy Picture of the Day
Blown
by fast winds from a hot, massive star, this cosmic bubble is
huge. Cataloged as Sharpless 2-308
it lies some 5,200 light-years away toward the constellation of the Big Dog (Canis Major)
and covers slightly more of the sky than a Full Moon.
That corresponds to
a diameter of 60 light-years at its estimated distance. The massive star that
created the bubble, a Wolf-Rayet star, is the
bright one near the center of the nebula.
Wolf-Rayet
stars have over 20 times the mass of the Sun and are thought to be in
a brief, pre-supernova
phase of massive star evolution.
Fast
winds from this Wolf-Rayet star create the bubble-shaped nebula as
they sweep up slower moving material from an earlier phase of evolution.
The windblown nebula has an
age of about 70,000
years. Relatively faint emission captured in the expansive image is
dominated by the glow of ionized oxygen atoms mapped
to a blue hue.
Image Credit & Copyright: Kfir Simon