Epoch J2000.0 Equinox J2000.0
|Right ascension||20h 21m 44.3s</ref>|
|Declination||+37° 22′ 30.56″|
|Apparent magnitude (V)||12.94|
|Apparent magnitude (J)||9.538|
|Apparent magnitude (H)||8.889|
|Apparent magnitude (K)||8.596|
|U−B color index||−0.29|
|B−V color index||+1.43|
|Proper motion (μ)||RA: -8.0 ± 5.4 mas/yr
Dec.: -2.8 ± 5.4 mas/yr
|Absolute magnitude (MV)||-2.49|
|Luminosity (bolometric)||245,000 L☉|
|Luminosity (visual, LV)||847 L☉|
|Metallicity [Fe/H]||0.0 dex|
|Rotational velocity (v sin i)||1,000 km/s|
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 it's light is very reddened and extinguished by interstellar dust.
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. Modelling the atmosphere gives a luminosity around 245,000 L☉, while calculations from brightness and distance give luminosities of 500,000 L☉or more. It is a very small dense star, with a radius 40% of the solar one but 20 times more massive. Very strong stellar winds, with a terminal velocity of 5,000 kilometers per second are causing WR 142 to lose 10−5 M☉/year. 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.
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). It is very likely that WR 142 is on its last stages of nuclear fusion, near or beyond the end of helium burning. It will explode as a supernova very soon in astronomical terms, within a few thousand years. The mass and rapid rotation make a GRB likely.
- Zacharias, N. et al. (2003). "The Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC2)". CDS/ADC Collection of Electronic Catalogues volume=1289. Bibcode:2003yCat.1289....0Z.
- 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.
- A bot will complete this citation soon. Click here to jump the queue arXiv:1507.00839v1.
- 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. doi:10.1086/131065. ISSN 0004-6280.
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- 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". arXiv:1308.4681v1 [astro-ph.SR].
- 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". arXiv:1401.7322 [astro.ph].