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Credit & Copyright: Bob Franke
Explanation:
Beautiful barred spiral
galaxy M109,
109th entry in Charles Messier's famous catalog of bright
Nebulae
and Star Clusters, is
found
just below the Big Dipper's bowl in the
northern constellation Ursa Major.
In telescopic views, its striking central bar gives the galaxy the
appearance of the Greek letter "theta", θ, a common mathematical
symbol representing an angle.
Of course M109 spans a very small
angle in planet
Earth's sky, about 7 arcminutes or 0.12 degrees.
But that small
angle
corresponds to an enormous 120,000 light-year diameter
at the galaxy's estimated 60 million light-year distance.
The brightest member of the now
recognized
Ursa Major galaxy
cluster, M109 (aka NGC 3992) is joined by
three spiky
foreground stars strung out
across this frame.
The three small, fuzzy bluish galaxies also on the scene, identified
left to right as UGC 6969, UGC 6940 and UGC 6923,
are possibly satellite galaxies of the larger M109.
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Based on Astronomy Picture
Of the Day