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][lower-alpha 1]

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

References

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[ru] Westerhout 49-2