Westerhout 49-2
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | 19h 10m 21.858s[1] |
| Declination | 09° 05′ 02.53″[1] |
| Characteristics | |
| Spectral type | O2-3.5If*[2] |
| Astrometry | |
| Distance | 36,200 ly (11,100[2] pc) |
| Details[2] | |
| Mass | 250±120 M☉ |
| Radius | 55.29[a] R☉ |
| Luminosity | 4,365,000 L☉ |
| Temperature | 35,500 K |
| Other designations | |
TIC 202340617, 2MASS J19102185+0905025 | |
| Database references | |
| SIMBAD | data |
Westerhout 49-2 (W49-2) is a very massive and luminous star in the H II region Westerhout 49. At a mass of 250 solar masses (although with significant uncertainty) and a luminosity of over 4 million L☉, it is one of the most massive and most luminous known stars.[2]
Properties
Westerhout 49-2 is located within the H II region Westerhout 49, about 11.1 kiloparsecs from the Sun. The star is heavily reddened, by nearly 5 magnitudes in the K band, the most of any star in the region. Westerhout 49-2 is classified as an evolved slash star, with a spectral type of O2-3.5If*. The star is one of the most luminous stars known, with a luminosity of 4,365,000 L☉, and has a temperature of about 35,500 K, corresponding to a radius of over 55 times that of the Sun.[2][a]
Uncertainties
There is significant uncertainty about Westerhout 49-2's properties. For example, its luminosity may be anywhere between 2,455,000 L☉ and 7,763,000 L☉. Moreover, there is even greater uncertainty about its mass, which may be anywhere between 110 and 370 M☉. Another estimate puts its mass between 90 and 240 M☉, but it uses a mass-luminosity relation instead of fitting models to the spectrum. Moreover, its mass is likely higher than the theoretical upper limit of 150 M☉, which means it could be a binary, if x-rays are detected. Westerhout 49-1, 49-2 and 49-12 are all bright x-ray sources, which means they could all be binary stars and their masses would be lower than the predicted mass if they were single stars.[2]
Notes
- ^ a b Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:
References
- ^ a b Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
- ^ a b c d e f Wu, Shi-Wei; Bik, Arjan; Bestenlehner, Joachim M.; Henning, Thomas; Pasquali, Anna; Brandner, Wolfgang; Stolte, Andrea (2016-05-01). "The massive stellar population of W49: A spectroscopic survey". Astronomy and Astrophysics. 589: A16. arXiv:1602.05190. Bibcode:2016A&A...589A..16W. doi:10.1051/0004-6361/201527823. ISSN 0004-6361. S2CID 59425112.
