| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion |
| Right ascension | 05h 05m 23.72142s[2] |
| Declination | +01° 10′ 39.4512″[2] |
| Apparent magnitude (V) | 4.4 - 6.9[3] |
| Characteristics | |
| Evolutionary stage | AGB |
| Spectral type | C-N5 C25.5[4](C5,4(N5)[5]) |
| U−Bcolor index | +6.84[6] |
| B−Vcolor index | +3.42[6] |
| Variable type | SRb[5] |
| Astrometry | |
| Radial velocity (Rv) | +16.50[7] km/s |
| Proper motion (μ) | RA: +7.5[2]mas/yr Dec.: -1.4[2]mas/yr |
| Parallax (π) | 2.65±0.95 mas[2] |
| Distance | approx. 1,200 ly (approx. 400 pc) |
| Absolute magnitude (MV) | −5.76[8] |
| Details | |
| Mass | 1-2[9] M☉ |
| Radius | 406[9] R☉ |
| Luminosity | 6,761[9] L☉ |
| Surface gravity (log g) | −0.60[9] cgs |
| Temperature | 2,600[9] K |
| Metallicity [Fe/H] | 0.0[9] dex |
| Other designations | |
| W Ori,BD+00°939,HD 32736,HIP 23680 | |
| Database references | |
| SIMBAD | data |
W Orionis is acarbon star in theconstellationOrion, approximately 400 parsecs (1,300 ly) away. It varies regularly in brightness between extremes ofmagnitude 4.4 and 6.9 roughly every 7 months. When it is near its maximum brightness, it is faintly visible to thenaked eye of an observer with good observing conditions.
Evelyn Leland discovered that the star is avariable star based on observations done in the last decades of the 19th century, when it was known as BD +00°939. The discovery was announced in 1895.[10] It was listed with itsvariable star designation, W Orionis, inAnnie Jump Cannon's 1907 workSecond Catalog of Variable Stars.[11]W Orionis is asemiregular variable with an approximately 212‑day cycle.[5] A long secondary period of 2,450 days has also been reported.[12]
The angular diameter of W Orionis has been measured usinginterferometry and a value of 9.7mas is found. Although it is known to be a pulsating variable star, no changes in the diameter were seen.[9]
Technetium has not been detected in W Orionis, an unexpected result since thiss-process element should bedredged up in all thermally-pulsating AGB stars and especially in carbon stars.[9]
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