Messier 106 (also known as NGC 4258) is a spiral galaxy in the constellation Canes Venatici. It was discovered by Pierre Méchain in 1781. M106 is at a distance of about 22 to 25 million light-years away from Earth. It is also a Seyfert II galaxy. Due to x-rays and unusual emission lines detected, it is suspected that part of the galaxy is falling into a supermassive black hole in the center. NGC 4217 is a possible companion galaxy of Messier 106. A Type II supernova was observed in this galaxy in May 2014.
M106 is one of the largest and brightest nearby galaxies, similar in size and luminosity to the Andromeda Galaxy. It has also played an important role in calibrating the cosmic distance ladder. Before, Cepheid variables from other galaxies cannot be used to measure distances since they cover ranges of metallicities different from the Milky Way's. M106 contains Cepheid variables similar to both of the metallicities of the Milky Way and other galaxies' Cepheids. By measuring the distance of the Cepheids with metallicities similar to our galaxy, astronomers are able to recalibrate the other Cepheids with different metallicities, a key fundamental step in improving the distances to other galaxies in the universe (source Wikipedia).
HaLRGB composition, total integration 8.5hrs, March 2015. William Optics FLT132 at F5.6 - Avalon Linear Fast Reverse - Atik 460EX - Baader LRGB and Astrodon 5nm NB filters.