The hottest: WR 102
WHILE STARS MAY not follow the exact ratio set by this quote from the 6th-century-b.c. Chinese work Tao Te Ching, the gist holds true. The faster a star burns through its fuel, the shorter its life. And this is surely the case for Wolf-Rayet stars. These stars not only burn incredibly hot and bright, but their stellar winds also blast much of their potential fuel into space. The hottest known star, WR 102, is one such Wolf-Rayet, sporting a surface temperature more than 35 times hotter than the Sun.
Like Baskin-Robbins, Wolf-Rayet stars come in a variety of flavors. The most massive star, RMC 136a1, has a spectral type of WN, meaning it’s rich in ionized nitrogen as a result of rapidly converting hydrogen to helium in its fiery core via the C-N-O cycle.
However, the hottest star, WR 102, is an especially rare WO-type Wolf-Rayet, which is a late-stage star that has a surface heavily enriched with ionized oxygen. All said, astronomers only know of about 10 WO-type Wolf-Rayet stars in the entire universe.
Even for a Wolf-Rayet star, WR 102 has intense stellar winds. Currently, they are blowing about a Sun’s worth of mass from the star’s surface every 100,000 years. That means WR 102 is losing several hundred million times more mass each year than the Sun. Although that may not seem like much for a massive star, keep in mind that at this rate, WR 102 would be completely gone in less than 2 million years. But who can wait that long?
Astronomers are interested in WR 102 not just because of its exceptionally hellish surface temperature and rapid mass loss, but also because the star is a prime candidate to go supernova in the relatively near future. In a 2015 paper that explored how much time a variety of WO-type Wolf-Rayets have left before exploding as supernovae, WR 102 was found to have the worst prognosis.
According to the authors: “WR 102 is a post-core helium burning star and has a remaining lifetime of less than 2,000 years.”