WR 102
A rare, extremely hot Wolf–Rayet star nearing supernova.
WR 102 is a Wolf–Rayet star in the constellation Sagittarius, belonging to the extremely rare WO oxygen sequence. It is a luminous and very hot star, highly evolved and close to exploding as a supernova.
Quick Facts
- Spectral classification
- WO2
- Surface temperature
- 210,000 K
- Terminal wind velocity
- 5,000 kilometers per second
- Mass loss rate
- 10^-5 solar masses per year
Facts from the source article.
Discovery
WR 102 was first noted as a possible optical counterpart to the X-ray source GX 3+1, but it was soon recognized as a separate object. In 1971 it was highlighted for its unusual OVI emission lines and classified as a WC star, though it was not the central star of a planetary nebula. It received the variable star designation V3893 Sagittarii. Faint nebulosity around it was discovered in 1981, and in 1982 it helped define the WO class of Wolf–Rayet stars.
Features
WR 102 is a Wolf–Rayet star on the oxygen sequence, one of only four known in the Milky Way and nine in other galaxies. Its surface temperature reaches 210,000 K, making it one of the hottest stars known. Atmospheric modeling and calculations from brightness and distance (assuming roughly 200,000 K) give its luminosity, while its origin is likely the Sagittarius OB5 association. This small, dense star loses about 10⁻⁵ solar masses per year through winds traveling at 5,000 km/s, a loss rate hundreds of millions of times greater than the Sun's. Those winds and intense ultraviolet radiation have shaped surrounding gas into a bubble-like Wolf–Rayet nebula.
Evolutionary status
WO stars represent the final evolutionary stage of the most massive stars before supernova. WR 102 is likely near or past the end of helium burning and is calculated to explode as a supernova within 1,500 years. A gamma-ray burst would be possible if it is rapidly rotating, but spectropolarimetric observations suggest its rotation speed is much lower than earlier estimates of 1,000 km/s.
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