WR 142

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WR 142
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cygnus
Right ascension 20h 21m 44.3s[1]
Declination +37° 22′ 30.56″[1]
Apparent magnitude (V) 12.94[2]
Spectral type WO2[3]
Apparent magnitude (J) 9.538[1]
Apparent magnitude (H) 8.889[1]
Apparent magnitude (K) 8.596[1]
U−B color index −0.29[4]
B−V color index +1.43[5]
Proper motion (μ) RA: −8.0 ± 5.4[1] mas/yr
Dec.: −.8 ± 5.4[1] mas/yr
Distance 4,000 ly
(1,230[2] pc)
Absolute magnitude (MV) -2.49[2]
Mass 20[2] M
Radius 0.40[3] R
Luminosity (bolometric) 245,000[3] L
Luminosity (visual, LV) 847[2] L
Temperature 200,000[3] K
Metallicity [Fe/H] 0.0[3] dex
Rotational velocity (v sin i) 1,000[2] km/s
Other designations
WR 142, 2MASS J20214434+3722306, GSC 02684-00001, Sand 5, St 3, UCAC2 44891902
Database references

WR 142 is a Wolf-Rayet star in the constellation Cygnus, an extremely rare star on the WO oxygen sequence.


WR 142 is usually assumed to be a member of the open cluster Berkeley 87, whose distance from the Sun is not very well known but thought to be around 1.23 kiloparsecs (4,000 light-years). As with its home cluster its light is very reddened and extinguished by interstellar dust.[6]

This star, 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 one of the hottest known with a surface temperature of 200,000 K.[3] Modelling the atmosphere gives a luminosity around 245,000 L, while calculations from brightness and distance give luminosities of 500,000 Lor more. It is a very small dense star, with a radius 40% of the Sun's but a mass 20 times greater. Very strong stellar winds, with a terminal velocity of 5,000 kilometers per second are causing WR 142 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 142.

Hard X-Ray emission has been detected from this star with the help of the Chandra space telescope, that has been suggested to be caused by the presence of a companion, a B-type main sequence star located at a distance of 1 AU from WR 142. There is no other indication of a companion and other reasons for the x-ray luminosity are considered more likely.[6]

Evolutionary status[edit]

WO Wolf-Rayet stars are the last evolutionary stage of the most massive stars before exploding as supernovae, possibly with a gamma-ray burst (GRB).[7] It is very likely that WR 142 is on its last stages of nuclear fusion, near or beyond the end of helium burning.[8] It is estimated to explode as a supernova in approximately 2,000 years. The mass and rapid rotation make a GRB likely.[3]

See also[edit]


  1. ^ a b c d e f g Zacharias, N.; et al. (2003). "The Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC2)". CDS/ADC Collection of Electronic Catalogues 1289: 0. Bibcode:2003yCat.1289....0Z. 
  2. ^ a b c d e f g Sander, A.; Hamann, W. -R.; Todt, H. (2012). "The Galactic WC stars". Astronomy & Astrophysics 540: A144. arXiv:1201.6354. Bibcode:2012A&A...540A.144S. doi:10.1051/0004-6361/201117830. 
  3. ^ a b c d e f g 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". Astronomy & Astrophysics 581 (110): A110. arXiv:1507.00839v1. Bibcode:2015A&A...581A.110T. doi:10.1051/0004-6361/201425390. 
  4. ^ Turner, D. G.; Forbes, D. (1982). "Berkeley 87, a heavily-obscured young cluster associated with the ON2 star-formation complex and containing the WO star Stephenson 3". Publications of the Astronomical Society of the Pacific 94: 789. Bibcode:1982PASP...94..789T. doi:10.1086/131065. ISSN 0004-6280. 
  5. ^ Van Der Hucht, Karel A.; Conti, Peter S.; Lundström, Ingemar; Stenholm, Björn (1981). "The Sixth Catalogue of galactic Wolf-Rayet stars, their past and present". Space Science Reviews 28 (3): 227–306. Bibcode:1981SSRv...28..227V. doi:10.1007/BF00173260. ISSN 0038-6308. 
  6. ^ a b Sokal, Kimberly R.; Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel; Schmutz, Werner (2010). "Chandra Detects the Rare Oxygen-type Wolf-Rayet Star WR 142 and OB Stars in Berkeley 87". The Astrophysical Journal 715 (2): 1327–1337. arXiv:1004.0462. Bibcode:2010ApJ...715.1327S. doi:10.1088/0004-637X/715/2/1327. 
  7. ^ 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". Astronomy & Astrophysics 558: A131. arXiv:1308.4681v1. Bibcode:2013A&A...558A.131G. doi:10.1051/0004-6361/201321906. 
  8. ^ Groh, Jose (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". Astronomy & Astrophysics 564: A30. arXiv:1401.7322. Bibcode:2014A&A...564A..30G. doi:10.1051/0004-6361/201322573.