NGC 3184

NGC 3184, also known as The Little Pinwheel Galaxy, is an unbarred spiral galaxy approximately 40 million light-years away in the constellation Ursa Major. Its name comes from its resemblance to the Pinwheel Galaxy. It was discovered by German-British astronomer William Herschel on 18 March 1787. It has two HII regions named NGC 3180 and NGC 3181.
NGC 3184 houses a high abundance of heavy elements. The blue color of its spiral arms comes mostly from relatively few bright young blue stars. The bright stars that highlight the arms were created in huge density waves that circle the center.

Structure

NGC 3184 has two prominent spiral arms. They have constant pitch angles, which makes them both symmetrical.

Six supernovae and astronomical transients have been observed in NGC 3184:SN 1921B was discovered by Fritz Zwicky on 6 April 1921.SN 1921C was discovered on 5 December 1921.SN 1937F was discovered by Rebecca Jones on 9 December 1937. SN 1999gi was discovered by Reiki Kushida on 9 December 1999.SN 2010dn was discovered by Kōichi Itagaki on 31 May 2010.SN 2016bkv was discovered by Kōichi Itagaki on 21 March 2016.

On May 31, 2010, Kōichi Itagaki detected a magnitude 17 optical transient 33" east and 61" north of the center of NGC 3184 at coordinates 10 18 19.89 +41 26 28.8. Designated SN 2010dn, this event was initially thought to be an outbursting luminous blue variable star, but later analysis categorized it as an intermediate-luminosity red transient, also known as a luminous red nova. Archival Hubble and Spitzer images of NGC 3184 seem to show no progenitor for optical transient SN 2010dn. SN 2010dn is just like SN 2008S and NGC 300-OT. On day 2, SN 2010dn had an unfiltered magnitude of 17.1, corresponding to a peak absolute magnitude of roughly -13.3.