During the January 2004 American Astronomical Society meeting in Atlanta, Stephen Eikenberry, a professor in the Infrared Astrophysics group at the University of Florida, claimed to have identified the largest and brightest star ever discovered.
The star, named LBV 1806–20, is a luminous blue variable located in northern Sagittarius. It is located approximately 45,000 light years away on the opposite side of the Milky Way from Earth. Dust clouds obscure visible light from the star; however, it is visible by infrared. Eikenberry's team shows that LBV 1806-20 may discharge up to 40 million times as much energy as our Sun. The previous largest know stars (Eta Carinae and the Pistol Star) measure in at only 6 million solar luminosities).
LBV 1806–20's infrared spectrum allows calculation of its temperature, between 18,000 to 32,000 kelvins. Its diameter is at least 200 times larger than our Sun's, and its mass may be more than 150 solar masses.
According to theory, a star cannot persist with more than about 100 or 120 solar masses. A star's mass is directly proportional to its luminosity, and a star above the 120 solar mass limit should emit so much energy that the pressure of this emission would eject much of its mass. Eikenberry suggests that LBV 1806–20 is a very young star that is doing just that.
Its closest neighbors include three rare Wolf-Rayet stars (hot stars that have ejected their outer hydrogen layers), a massive star forming inside a dust cloud, and a neutron star, formed from a supernova. Eikenberry suggests that the birth of these exceptionally huge stars may have resulted from a dense cloud of interstellar matter that was violently compacted during the supernova explosion.
Source: Sky and Telescope