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Star in the constellation Orion From Wikipedia, the free encyclopedia
W Orionis is a carbon star in the constellation Orion, approximately 400 parsecs (1,300 ly) away. It varies regularly in brightness between extremes of magnitude 4.4 and 6.9 roughly every 7 months.
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−B color index | +6.84[6] |
B−V color 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 | |
Database references | |
SIMBAD | data |
W Orionis is a semiregular variable with an approximately 212‑day cycle.[5] A long secondary period of 2,450 days has also been reported.[10]
The angular diameter of W Orionis has been measured using interferometry and a value of 9.7 mas 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 this s-process element should be dredged up in all thermally-pulsating AGB stars and especially in carbon stars.[9]