October 14, 2013
NGC 4145, a spiral galaxy in Canes Venatici
Image Credit & Copyright: Adam Block/NOAO/AURA/NSF/Mount Lemmon SkyCenter/University of Arizona (http://skycenter.arizona.edu/gallery)
NGC 4145 is a barred spiral galaxy that measures roughly 80,000 x 55,000 light-years, located about 46 million light-years away from Earth in the northern constellation of Canes Venatici (the Hunting Dogs). It is receding from us at approximately 1009 kilometers per second.
It has already made most of its stars and has little star-forming activity. While the spiral arms of this galaxy are punctuated by some activity, the rest of the galaxy is quite quiet. Astronomers suggest that a galaxy like this will soon (in galactic terms) lose the impetus to form stars and settle down to become a lenticular galaxy.
NGC 4145 has two satellite galaxies: the spiral galaxy NGC 4145A-1 (PGC 38778) and the very small NGC 4145A-2 (PGC 213942), and it is sometimes thought that it is interacting with NGC 4151 (the Eye of Sauron), an intermediate spiral Seyfert galaxy.
If that is true, this may help maintain the star formation in NGC 4145. In fact close inspection of the nucleus of NGC 4145 seems to indicate that the tug of NGC 4151 has displaced it from its position in the center of NGC 4145.