This grand design spiral galaxy, also known as NGC 3631, is located 80 million light years away in the constellation of Ursa Major at a declination of +53 degrees. It is a magnitude 10 galaxy that spans 4 arc-minutes in our apparent view, which corresponds to a diameter of 90,000 light years. We are looking at this galaxy at about 20 degrees from face-on.
In his
Arp catalog, Dr. Arp classified this object into the category of Spiral Galaxies with One Heavy Arm. The “Heavy Arm” categorization doesn’t make much sense to me. Both arms seem about equally "heavy" to me.
I like the interesting long and straight portion of the top arm. It appears to be part of a
Vorontsov-Velyaminov row. In addition, numerous blue star clusters are visible throughout the disk. Both of these, the clusters and the straight arm, are often signs of some type of gravitation interaction with another galaxy companion, but none is seen here. Perhaps the companion occurred long ago and has been absorbed into the disk. That is the most convenient explanation, whenever we don't understand something. Sort of like dark matter.
The mouseover comparison shows my image next to the Arp and Hubble images.
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