WR 102ka

WR 102ka, also known as the Peony star, is a Wolf–Rayet star that is one of several candidates for the most luminous-known star in the Milky Way.

WR 102ka

The "Peony Nebula," as discovered by NASA's Spitzer Space Telescope. This three-color infrared composite shows 3.6-micrometre light in blue, 8-micrometre light in green, and 24-micrometre light in red. The Peony nebula is the reddish cloud of dust in and around the white circle, surrounding the Peony nebular star.
Observation data
Epoch J2000.      Equinox J2000.
Constellation Sagittarius
Right ascension  17h 46m 18.12s[1]
Declination −29° 01′ 36.5″[1]
Characteristics
Evolutionary stage Slash star
Spectral type Ofpe/WN9[2]
Apparent magnitude (J) 13.0[1]
Apparent magnitude (H) 10.3[1]
Apparent magnitude (K) 8.8[1]
J−H color index 2.7[1]
J−K color index 4.2[1]
Variable type
Astrometry
Distance26k[2] ly
(8k[2] pc)
Details
Mass~100[3] M☉
Radius92[2] R☉
Luminosity3.2 million[2] L☉
Temperature25,100[2] K
Age<3[2] Myr
Other designations
Peony Star,[4] Peony nebula star, WR 102ka, 2MASS J17461811-2901366, ISOGAL-P J174618.2-290136, MSX6C G000.0003-00.1743
Database references
SIMBADdata

Discovery

WR 102ka lies near the Galactic Center and is essentially totally obscured in visible wavelengths. Thus it must be observed in longer wavelength infrared light, which is able to penetrate the dust. WR 102ka was catalogued in 2002 and 2003 by infrared surveys. It was observed for the Two-Micron All Sky Survey (2MASS) in the near-infrared J, H, and Ks bands, at 1.2 μm, 1.58 μm, and 2.2 μm, respectively,[1] and the ISOGAL survey of candidate young stellar objects at 7 μm and 15 μm.[5]

Narrowband infrared observations of several spectral features around 2 μm showed that WR 102ka was a Wolf Rayet star with a likely classification of WN10.[6] It was also proposed as a possible luminous blue variable.[7]

The Spitzer Space Telescope observed WR 102ka at wavelengths of 3.6 μm, 8 μm, and 24 μm on April 20, 2005. These observations allowed the first reliable calculations of the physical properties of this extremely luminous object.[2]

Other luminous Milky Way stars

An even more luminous yet closer star, WR 25, appears to be most likely to the title. Another nearer star, Eta Carinae, which was the second-brightest star in the sky for a few years in the 19th century, appears to be slightly more luminous than WR 102ka, but is known to be a binary star system. There is also the more recently discovered Pistol Star that, like the Peony star, derives its name from the shape of the nebula in which it is embedded, and which it has probably created through heavy mass loss via fierce stellar winds and perhaps also major "mini-supernova-like" eruptions as happened to Eta Carinae around the 1830s–1840s creating the lobes observed by the Hubble Space Telescope.

The luminosities of the Pistol Star, Eta Carinae, and WR 102ka are all rendered somewhat uncertain due to heavy obscuration by galactic dust in the foreground, the effects of which must be corrected for before their apparent brightness can be reduced to estimate their total radiated power or bolometric luminosity. Both Eta Carinae and WR 102ka are believed likely to explode as supernovas or hypernovae within the next few million years. As is typical of such extremely massive and luminous stars, both have expelled a considerable portion of their initial mass, when originally formed, in dense, massive stellar winds.

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See also

References
  1. Skrutskie, M. F.; et al. (2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163. Bibcode:2006AJ....131.1163S. doi:10.1086/498708.
  2. Barniske, A.; Oskinova, L. M.; Hamann, W. -R. (2008). "Two extremely luminous WN stars in the Galactic center with circumstellar emission from dust and gas". Astronomy and Astrophysics. 486 (3): 971. arXiv:0807.2476. Bibcode:2008A&A...486..971B. doi:10.1051/0004-6361:200809568.
  3. Oskinova, L. M.; Steinke, M.; Hamann, W. - R.; Sander, A.; Todt, H.; Liermann, A. (2013). "One of the most massive stars in the Galaxy may have formed in isolation". Monthly Notices of the Royal Astronomical Society. 436 (4): 3357. arXiv:1309.7651. Bibcode:2013MNRAS.436.3357O. doi:10.1093/mnras/stt1817.
  4. Wolf-Rainer Hamann; Andreas Barniske; Adriane Liermann; et al. (2011). "The most luminous stars in the Galaxy and the Magellanic Clouds". Société Royale des Sciences de Liège. 80: 98. arXiv:1012.1875v1. Bibcode:2011BSRSL..80...98H.
  5. Felli, M.; Testi, L.; Schuller, F.; Omont, A. (2002). "Young massive stars in the ISOGAL survey. II. The catalogue of bright YSO candidates". Astronomy and Astrophysics. 392 (3): 971–990. arXiv:astro-ph/9905296. Bibcode:2002A&A...392..971F. doi:10.1051/0004-6361:20020973.
  6. Homeier, N. L.; Blum, R. D.; Pasquali, A.; Conti, P. S.; Damineli, A. (2003). "Results from a near infrared search for emission-line stars in the Inner Galaxy: Spectra of new Wolf-Rayet stars". Astronomy & Astrophysics. 408: 153–159. arXiv:astro-ph/0306578. Bibcode:2003A&A...408..153H. doi:10.1051/0004-6361:20030989.
  7. Clark, J. S.; Larionov, V. M.; Arkharov, A. (2005). "On the population of galactic Luminous Blue Variables" (PDF). Astronomy & Astrophysics. 435: 239–246. Bibcode:2005A&A...435..239C. doi:10.1051/0004-6361:20042563.
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