Epoch J2000 Equinox J2000
|Right ascension||05h 05m 23.72142s|
|Declination||+01° 10′ 39.4512″|
|Apparent magnitude (V)||4.4 - 6.9|
|Spectral type||C-N5 C25.5 (C5,4(N5))|
|U−B color index||+6.84|
|B−V color index||+3.42|
|Radial velocity (Rv)||+16.50 km/s|
|Proper motion (μ)|| RA: +7.5 mas/yr |
Dec.: -1.4 mas/yr
|Parallax (π)||2.65 ± 0.95 mas|
|Distance||approx. 1,200 ly |
(approx. 400 pc)
|Absolute magnitude (MV)||−5.76|
|Surface gravity (log g)||−0.60 cgs|
|Metallicity [Fe/H]||0.0 dex|
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.
W Orionis is a semiregular variable with an approximately 212‑day cycle. A long secondary period of 2,450 days has also been reported.
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.
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.