Explanation:
Big, beautiful spiral galaxy M101 is one of the last
entries in Charles
Messier's famous catalog, but definitely not
one
of the least.
About 170,000 light-years across, this galaxy is enormous,
almost twice the size of our own Milky Way galaxy.
M101 was also one of the original
spiral
nebulae observed by Lord Rosse's large
19th century
telescope, the Leviathan of Parsontown.
This
mosaic of M101
was assembled from Hubble Legacy Archive data.
Additional ground-based data was included to further define
the telltale reddish emission from atomic hydrogen gas in
this gorgeous galaxy's star forming regions.
The sharp image shows stunning features in the galaxy's
face-on disk of stars and dust along with background galaxies,
some visible right through M101 itself.
Also known as the
Pinwheel Galaxy,
M101 lies within
the boundaries of the northern constellation
Ursa Major,
about 25 million light-years away.
