WR 156
Young massive and luminous star in the constellation Cepheus
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WR 156 is a young massive and luminous Wolf–Rayet star in the constellation of Cepheus. Although it shows a WR spectrum, it is thought to be a young star still fusing hydrogen in its core.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus[1] |
| Right ascension | 23h 00m 10.12539s[2] |
| Declination | +60° 55′ 38.4109″[2] |
| Apparent magnitude (V) | 11.01[3] |
| Characteristics | |
| Evolutionary stage | Wolf-Rayet[4] |
| Spectral type | WN8h[5] |
| B−V color index | +1.17[3] |
| Astrometry | |
| Proper motion (μ) | RA: −2.596[2] mas/yr Dec.: −1.768[2] mas/yr |
| Parallax (π) | 0.2749±0.0125 mas[2] |
| Distance | 11,900 ± 500 ly (3,600 ± 200 pc) |
| Absolute magnitude (MV) | −7.00[6] |
| Details | |
| Mass | 32[6] M☉ |
| Radius | 20.81[6] R☉ |
| Luminosity | 1,023,000[6] L☉ |
| Temperature | 39,800[6] K |
| Other designations | |
| WR 156, HIP 113569, 2MASS J23001010+6055385, MR 119 | |
| Database references | |
| SIMBAD | data |
Distance
WR 156 has a Hipparcos parallax of 3.16" indicating a distance of about a thousand light years, although with a fairly large margin of error. Other studies indicate that it is much more distant based on a very high luminosity and faint apparent magnitude.[6] The Gaia DR1 parallax is 0.07". The margin of error is larger than the measured parallax, but still the indication is for a very large distance.[7] In Gaia Data Release 2, the parallax is given as 0.2090±0.0251 mas but with a marker that the result may be unreliable.[8] In Gaia Data Release 3, the solution was adjusted to 0.2749±0.0125 mas, still with significant astrometric noise excess.[2]
Physical properties
WR 156 has a WR spectrum on the nitrogen sequence, indicating strong emission of helium and nitrogen, but it also shows features of hydrogen. Therefore, it is given a spectral type of WN8h. Its outer layers are calculated to contain 30% hydrogen, one of the highest levels for any galactic Wolf Rayet star.[4]
WR 156 has a low temperature and slow stellar wind by Wolf Rayet standards, only 39,800 K and 660 km/s respectively. The wind is very dense, with total mass loss of more than 1/100,000 M☉/year.[6]
WR 156 is a young hydrogen-rich star, still burning hydrogen in its core but sufficiently luminous to have convected up nitrogen and helium fusion products to its surface. It shows 27% hydrogen at its surface.[6] It is estimated to have had an initial mass of 50 M☉ several million years ago.[4]