Luminous Blue Variables (sometimes known as LBV stars) are probably one of my favourite types of star. Simply, they’re awe inspiring. As with all the most interesting things in the night sky, they’re also very rare, with only a handful having been discovered.
A luminous blue is a type of hypergiant. A furious stellar giant, with up to 150 times the Sun’s mass. They hold a place amongst the most luminous stars known, easily shining with millions of times the brightness of the Sun. Their huge mass drives nuclear reactions within them to produce prodigous amounts of energy. So much in fact, that most luminous blues are in danger of tearing themselves apart.
The immense stellar wind generated by the rage of these stars, combined with their violently energetic nature causes them to steadily lose mass. Stellar material is constantly thrown off into surrounding space at thousands of kilometres per second, causing these stars to reside in nebular cocoons of their own material.
Needless to say, such a star can’t survive for very long. To use the cliché, luminous blues live fast and die young, only surviving for a few million years. Exactly what happens in the life of a luminous blue isn’t entirely certain. Simply, we haven’t seen enough of them to know for sure. That said, many believe they will evolve into similarly enraged Wolf-Rayet stars, before exploding as supernovae.
A few well known luminous blues include Eta Carinae, S Doradus, P Cygni and the Pistol Star. All are among the most massive and the most luminous stars known (although the debate over which star is actually most luminous, and whether it is indeed an LBV is still open). The Pistol Star, in fact, is so luminous that it emits roughly the same amount of energy in 20 seconds as the Sun does in a year!