Canis Major
Canis Major contains Sirius, the brightest star in the night sky, known as the "dog star". It is bright because of its proximity to the Solar System. In contrast, the other bright stars of the constellation are stars of great distance and high luminosity. At magnitude 1.5, Epsilon Canis Majoris (Adhara) is the second-brightest star of the constellation and the brightest source of extreme ultraviolet radiation in the night sky. Next in brightness are the yellow-white supergiant Delta (Wezen) at 1.8, the blue-white giant Beta (Mirzam) at 2.0, blue-white supergiants Eta (Aludra) at 2.4 and Omicron at 3.0, and white spectroscopic binary Zeta (Furud), also at 3.0. The red hypergiant VY Canis Majoris is one of the largest stars known, while the neutron star RX J0720.4-3125 has a radius of a mere 5 km.
LBV 1806-20
When first discovered, LBV 1806-20 was considered both the most luminous and most massive star known, challenging our understanding of the formation of massive stars. Recent estimates place it somewhat nearer to Earth, which when combined with its binary nature mean that it is now well within the expected range of parameters for extremely luminous stars in the galaxy. It is estimated at 2 million times as luminous as the sun which makes it one of the most luminous stars in the galaxy.
LBV 1806-20 lies at the core of radio nebula G10.0–0.3, which is believed to be primarily powered by its stellar wind. It is a member of the 1806-20 open cluster, itself a component of W31, one of the largest H II regions in the Milky Way. Cluster 1806-20 is made up of some highly unusual stars, including four Wolf–Rayet stars, several OB stars, and a magnetar (SGR 1806-20).