WR 102

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
WR 102
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagittarius
Right ascension 17h 45m 47.5s[1]
Declination −26° 10′ 27″[1]
Apparent magnitude (V) 14.10[2]
Evolutionary stage Wolf-Rayet star
Spectral type WO2[3]
B−V color index +0.77[4]
Distance 5,560[5] pc
Absolute magnitude (MV) −1.71[2]
Mass 19[2] M
Radius 0.39[3] R
Luminosity 282,000[3] L
Temperature 210,000[3] K
Metallicity [Fe/H] 0.0[3] dex
Rotational velocity (v sin i) 1,000[2] km/s
Other designations
V3893 Sagittarii, LS 4368, ALS 4368, Sand 4
Database references

WR 102 is a Wolf-Rayet star in the constellation Sagittarius, an extremely rare star on the WO oxygen sequence.


Infrared image of the nebulosity around WR102 (WISE)

WR 102, of spectral classification WO2, is one of the very few known oxygen-sequence Wolf-Rayet stars, just four in the Milky Way galaxy and five in external galaxies. It is also the hottest known with a surface temperature of 210,000 K. Modelling the atmosphere gives a luminosity around 282,000 L,[3] while calculations from brightness and distance gives luminosity of nearly 500,000 L although the distance is not known with any certainty.[2] It is a very small dense star, less than 0.4 R but nearly 20 M.

Very strong stellar winds with a terminal velocity of 5,000 kilometers per second are causing WR 102 to lose 10−5 M/year.[2] For comparison, the Sun loses (2-3) x 10−14 solar masses per year due to its solar wind, several hundred million times less than WR 102. These winds and the strong ultraviolet radiation from the hot star have compressed and ionised the surrounding interstellar material into a complex series of arcs described as the bubble type of Wolf-Rayet nebula.[6]

Evolutionary status[edit]

WO stars are the last evolutionary stage of the most massive stars before exploding as supernovae.[7] It is very likely that WR 102 is on its last stages of nuclear fusion, near or beyond the end of helium burning.[8]

It has been calculated that WR 102 will explode as a supernova within 1,500 years.[3] High mass and rapid rotation would make a gamma-ray burst (GRB) possible,[7] but it is unclear if WR 102 is rotating rapidly.[3]

See also[edit]


  1. ^ a b Dufton, P. L.; Smartt, S. J.; Hambly, N. C. (2001). "A UKST survey of blue objects towards the Galactic centre - seven additional fields" (PDF). Astronomy and Astrophysics. 373 (2): 608–624. Bibcode:2001A&A...373..608D. doi:10.1051/0004-6361:20010613. ISSN 0004-6361. 
  2. ^ a b c d e f Sander, A.; Hamann, W. -R.; Todt, H. (2012). "The Galactic WC stars" (PDF). Astronomy & Astrophysics. 540: A144. arXiv:1201.6354Freely accessible. Bibcode:2012A&A...540A.144S. doi:10.1051/0004-6361/201117830. 
  3. ^ a b c d e f g h Tramper, F.; Straal, S. M.; Sanyal, D.; Sana, H.; de Koter, A.; Gräfener, G.; Langer, N.; Vink, J. S.; de Mink, S. E.; Kaper, L. (2015). "Massive stars on the verge of exploding: The properties of oxygen sequence Wolf-Rayet stars" (PDF). Astronomy & Astrophysics. 581 (110): A110. arXiv:1507.00839v1Freely accessible. Bibcode:2015A&A...581A.110T. doi:10.1051/0004-6361/201425390. 
  4. ^ Smith, Lindsey F.; Shara, Michael M.; Moffat, Anthony F. J. (1990). "Distances of Galactic WC stars from emission-line fluxes and a quantification of the WC classification". The Astrophysical Journal. 358: 229. Bibcode:1990ApJ...358..229S. doi:10.1086/168978. ISSN 0004-637X. 
  5. ^ van der Hucht, Karel A. (2001). "The VIIth catalogue of galactic Wolf–Rayet stars". New Astronomy Reviews. 45 (3): 135–232. Bibcode:2001NewAR..45..135V. doi:10.1016/S1387-6473(00)00112-3. ISSN 1387-6473. 
  6. ^ Toalá, J. A.; Guerrero, M. A.; Ramos-Larios, G.; Guzmán, V. (2015). "WISE morphological study of Wolf-Rayet nebulae" (PDF). Astronomy & Astrophysics. 578: A66. arXiv:1503.06878Freely accessible. Bibcode:2015A&A...578A..66T. doi:10.1051/0004-6361/201525706. 
  7. ^ a b Groh, Jose H.; Meynet, Georges; Georgy, Cyril; Ekstrom, Sylvia (2013). "Fundamental properties of core-collapse Supernova and GRB progenitors: Predicting the look of massive stars before death" (PDF). Astronomy & Astrophysics. 558: A131. arXiv:1308.4681v1Freely accessible. Bibcode:2013A&A...558A.131G. doi:10.1051/0004-6361/201321906. 
  8. ^ Groh, Jose H.; Meynet, Georges; Ekström, Sylvia; Georgy, Cyril (2014). "The evolution of massive stars and their spectra I. A non-rotating 60 Msun star from the zero-age main sequence to the pre-supernova stage" (PDF). Astronomy & Astrophysics. 564: A30. arXiv:1401.7322Freely accessible. Bibcode:2014A&A...564A..30G. doi:10.1051/0004-6361/201322573.