Explanation:
Big and beautiful
spiral galaxy M81
lies in the northern constellation
Ursa Major.
One of the
brightest galaxies in planet Earth's sky, M81 is also home
to the second brightest
supernova seen in modern times.
This superbly
detailed view
reveals M81's bright yellow nucleus, blue
spiral arms, and sweeping cosmic dust lanes with a scale comparable to
the
Milky Way.
Hinting at a disorderly past,
a remarkable dust lane actually runs straight through the
disk, below and right of the galactic center,
contrary to
M81's
other prominent
spiral features.
The errant
dust lane may be the lingering result of
a close encounter between
M81 and its smaller companion galaxy, M82.
Scrutiny of variable stars in M81 (aka NGC 3031)
has yielded one of the best
determined
distances for an external galaxy -- 11.8 million light-years.
