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.
Star
As of 2006, the star with the highest known absolute magnitude is LBV 1806-20, with a magnitude of −14.2. This star is at least 5,000,000 times more luminous than the Sun. The least luminous stars that are currently known are located in the NGC 6397 cluster. The faintest red dwarfs in the cluster were magnitude 26, while a 28th magnitude white dwarf was also discovered. These faint stars are so dim that their light is as bright as a birthday candle on the Moon when viewed from the Earth.