M74
Messier 74 (also known as NGC 628 and Phantom Galaxy) is a spiral galaxy in the constellation Pisces. It is at a distance of about 32 million light-years away from Earth. The galaxy contains two clearly defined spiral arms and is therefore used as an archetypal example of a grand design spiral galaxy. The galaxy's low surface brightness makes it the most difficult Messier object for amateur astronomers to observe. However, the relatively large angular size of the galaxy and the galaxy's face-on orientation make it an ideal object for professional astronomers who want to study spiral arm structure and spiral density waves. It is estimated that M74 is home to about 100 billion stars.
M74 was discovered by Pierre Méchain in 1780. Méchain then communicated his discovery to Charles Messier, who listed the galaxy in his catalogue
Three supernovae have been identified in M74: SN 2002ap, SN 2003gd, and SN 2013ej.
SN 2002ap has attracted considerable attention because it is one of the few Type Ic supernovae (or hypernovae) observed within 10 Mpc in recent years. This supernovae has been used to test theories on the origins of similar Type Ic supernovae at higher distances and theories on the connection between supernovae and gamma ray bursts.
SN 2003gd is a Type II-P supernova.[14] Type II supernovae have known luminosities, so they can be used to accurately measure distances. The distance measured to M74 using SN 2003gd is 9.6 ± 2.8 Mpc, or 31 ± 9 million ly. For comparison, distances measured using the brightest supergiants are 7.7 ± 1.7 Mpc and 9.6 ± 2.2 Mpc. Ben E. K. Sugerman found a "light echo" – a reflection of supernova explosion that appeared after the explosion itself – associated with SN 2003gd. This is one of the few supernovae in which such a reflection has been found. This reflection appears to be from dust in a sheet-like cloud that lies in front of the supernova, and it can be used to determine the composition of the interstellar dust.
M74 is the brightest member of the M74 Group, a group of 5–7 galaxies that also includes the peculiar spiral galaxy NGC 660 and a few irregular galaxies. Although different group identification methods may consistently identify many of the same member galaxies in this group, the exact group membership is still uncertain.
