Wolf–Rayet stars

Wolf–Rayet stars (often referred to as WR stars) are evolved, massive stars (over 20 solar masses when they were on the main sequence) which are losing mass rapidly by means of a very strong stellar wind, with speeds up to 2000 km/s. They typically lose 10−5 solar masses a year, a billion times faster than Sol.

Wolf–Rayet stars are extremely hot, with surface temperatures in the range of 30,000 K to around 200,000 K. They are also highly luminous, from tens of thousands to several million times the bolometric luminosity ofSol, although not exceptionally bright visually since most of their output is in far ultraviolet and even soft X-rays.

The naked eye stars Gamma Velorum and Theta Muscae, as well as the most massive known star, R136a1 in 30 Doradus, are all Wolf–Rayet stars.