Grand Spiral Galaxy M81
and Arp's Loop
One of the brightest
galaxies in planet Earth's sky is similar in size to our Milky Way Galaxy:
big, beautiful M81.
This grand spiral galaxy lies 11.8 million light-years away toward the northern
constellation of the Great Bear (Ursa Major).
The deep image of the
region reveals details in the bright yellow core, but at the same time follows
fainter features along the galaxy's gorgeous blue spiral arms and sweeping dust
lanes.
It also follows the
expansive, arcing feature, known as Arp's loop, that seems to rise from the
galaxy's disk at the upper right. Studied in the 1960s, Arp's loop has been
thought to be a tidal
tail, material pulled out of M81 by gravitational interaction with its
large neighboring galaxy
M82.
But a subsequent
investigation demonstrates that at least some of Arp's loop likely
lies within our own
galaxy. The loop's colors in visible and infrared light match the
colors of pervasive clouds
of dust, relatively unexplored
galactic cirrus only
a few hundred light-years above the plane of the Milky Way.
Along with the Milky
Way's stars, the dust clouds lie in the foreground of this remarkable view. M81's dwarf companion
galaxy, Holmberg
IX, can be seen just above the large spiral. On the sky, this image spans
about 0.5 degrees, about the size of the Full Moon.
Image Credit & Copyright: Bernard
Miller