About the Subject

M106 is a lovely, nearby spiral galaxy in the constellation Canes Venatici. Discovered in 1781 by Pierre Méchain , it was one of the last objects to be added to Messier's famous list of "not comets". It lies at a distance of roughly 24 lightyears from Earth. Unlike most of the Milky Way's neighbors, M106 has an active galactic nucleus, meaning its central black hole is consuming large amounts of material. This classifies M106 as a Type 2 Seyfert. 

As a result of the active nucleus, M106 has a very unusual characteristic that is prominent in radio frequencies and X-ray, but also detectable in visible light--a pair of "anomalous arms".  These arms lie between the regular spiral arms visible in most photographs of M106. The nature of these arms had been a mystery since their discovery in the 1960's. Originally, it was thought that these arms might be jets of particles from the central black hole, but follow-up observations in radio frequencies identified different jets coming from the core of M106, so that explanation didn't match the observations. It seemed unlikely that there could be more than one pair of jets coming from the black hole. 

Rather than being jets from the black hole itself, in 2001 it was proposed that the jets from the core of the galaxy might be heating gas in the disk of the galaxy, generating shock waves, and causing gas in the disk to glow in both X-ray and other frequencies. Archival data from the Spitzer space telescope and the Newton telescope were used in 2007 to confirm this theory. One of the two anomalous arms is visible in this image as well as portions of the second arm (faintly), as the anomalous arms do glow faintly in H-alpha.