WR 136 explained

WR 136 is a Wolf–Rayet star located in the constellation Cygnus. It is in the center of the Crescent Nebula. Its age is estimated to be around 4.7 million years and it is nearing the end of its life. Within a few hundred thousand years, it is expected to explode as a supernova.

According to recent estimations, WR 136 is 600,000 times brighter than the Sun, 21 times more massive, and 5.1 times larger. Its surface temperature is around 70,000 kelvins.

WR 136 blew off a shell of material with a mass of around when it became a red supergiant around 120,000–240,000 years ago and this is still expanding at 80 km/s.^[1] Currently, its fast stellar wind, ejected from the star at around 3.8 million mph (1,700 km/s^[2]), is catching up to the material ejected from the star and shaping it into a shell. Ultraviolet rays emitted from WR 136's hot surface cause the shell to glow.^[1]

There is some evidence WR 136 may be a binary star. Its companion would be a low-mass star of spectral classification K or M that would complete an orbit around the Wolf-Rayet star each 5.13 days, being the progenitor of a low-mass X-ray binary system.^[3]

Further reading

• 10.1134/S1063773706060041. Stratification of optical emission from NGC 6888 as a trace of the interaction between Wolf-Rayet stellar wind and the shell of a red supergiant. Astronomy Letters. 32. 6. 406. 2006. Bychkov. K. V.. Sitnik. T. G.. 2006AstL...32..406B. 123039046.

External links

• http://chandra.harvard.edu/photo/2003/ngc6888/
• http://www.giga-parsec.de/WRspectra.html
• http://www.castfvg.it/stelle/spettri/O/wr_136_01.htm

Notes and References

1. 2014ApJ...785..100M. The Trace of the CNO Cycle in the Ring Nebula NGC 6888. The Astrophysical Journal. 785. 2. 100. Mesa-Delgado. A.. Esteban. C.. García-Rojas. J.. Reyes-Pérez. J.. Morisset. C.. Bresolin. F.. 2014. 10.1088/0004-637X/785/2/100. 1402.6181 . 118596124.
2. 1994A&A...281..184H. Non-LTE spectral analyses of Wolf-Rayet stars: The nitrogen spectrum of the WN6 prototype HD 192163 (WR136). Astronomy and Astrophysics . 0004-6361. 281. 184. Hamann. W.-R.. Wessolowski. U.. Koesterke. L.. 1994.
3. The Wolf-Rayet star HD 192163 as a possible evolutionary progenitor of a low-mass X-ray binary . Rustamov . D. N. . Cherepashchuk . A. M. . . 55 . 4 . 347–358 . 2011ARep...55..347R . 17 July 2013 . 2011 . 10.1134/S1063772911010069 . 121379439 .