- ^ a b Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:
| 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]
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]
There is significant uncertainty about Westerhout 49-2's properties. One estimate using mass-luminosity relations finds a mass between 90 and 240 M☉. 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]
