Where are the hot stars in M81, one of the closest major spiral galaxies? To help find out, astronomers took a deep image in
ultraviolet light of the sprawling spiral with the Earth-orbiting
Galex telescope. Hot stars emit more ultraviolet than cool stars, and are frequently associated with young open clusters of stars and energetic star forming regions. Magnificent
spiral galaxy M81, slightly smaller in size to our own
Milky Way Galaxy, shows off its young stars in its winding spiral arms in the
above image. Less than 100 million years old, the young stars are blue in the
above false-color Galex image and seen to be well separated from the older yellowish stars of the galactic core. Visible above M81 is a satellite galaxy dubbed
Holmberg IX. Studying the unexpectedly bright ultraviolet glow of this small
irregular galaxy may help astronomers understand how the
many satellites of our own Milky Way Galaxy developed.
M81, visible through a small telescope, spans about 70,000
light years and lies about 12 million light years away toward the
constellation of the Great Bear (
Ursa Major).
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