Wolf–Rayet star
evolved, massive star that has run out of hydrogen / From Wikipedia, the free encyclopedia
Wolf–Rayet stars (WR stars) are massive stars (over 20 solar masses initially). They are losing mass rapidly by means of a very strong stellar wind, with speeds up to 2000 km/s. While our own Sun loses about 10−14 solar masses every year, Wolf–Rayet stars typically lose 10−5 solar masses a year.[1] (The last number is one million times larger than the second-to-last number.)
Wolf–Rayet stars are extremely hot, with surface temperatures in the range of 30,000 K to around 200,000 K that make them look blue in color.[2] They are also highly luminous, from tens of thousands to several million times the bolometric luminosity of the Sun, although not exceptionally bright visually since most of their output is in far[needs to be explained] ultraviolet and even "soft" X-rays.[3]