Messier 81
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Messier 81

April 15, 2005
The great spiral galaxy M81, similar in size and brightness to our Milky Way galaxy, is in the lower half of the image. The stars in its spiral arms have formed within the last 100 million years, as have most of the stars in a nearby dwarf galaxy just to the left of M81.

GALEX reveals that star formation is occurring quite distant from the nucleus of M81 in the faint blue extensions to the brighter spiral arms.

The nucleus, or center of M81, shines from the light of 10 billion year old stars near the end of their lives, which produce their energy by burning helium into carbon. These stars are cooler (and thus appear more red) then the younger hotter stars in the spiral arms of M81.

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