73 Orionis, a blue-white giant star in Orion
73 Orionis is a blue-white giant star in the constellation Orion. At 1,392 light years away, it shines at an apparent visual magnitude of 5.47.
73 Orionis (HIP 29736)
73 Orionis is a blue-white giant star in the constellation Orion. At 1,392 light years away, it shines at an apparent visual magnitude of 5.47. It is moving through the Galaxy at a speed of 13.6 km/s relative to the Sun.
Sky position: RA 6h 15.7m, Dec +12° 33.1'
Common designations: 73 Orionis, HR 2229, HD 43247, HIP 29736, Gaia DR3 3332037694121800960
73 Orionis has the spectral type B9II-III. B-type stars are hot (about 10,000 to 30,000 K), luminous and blue-white. They are massive, short-lived stars, typically only tens of millions of years old, and are common in young clusters and OB associations. Its luminosity class III marks it as a giant: an evolved star that has left the main sequence and swollen to many times its original size.
How to find 73 Orionis in the sky
73 Orionis lies in Orion. With a declination of +12° 33.1', it is visible from the entire Northern Hemisphere and from the Southern Hemisphere down to about latitude 77° S. It is bright enough to see with the naked eye under dark skies. It is highest in the sky at local midnight around January, which makes the weeks around that month the best time to observe it.
Tabulated data for 73 Orionis
Astrometry and spectroscopy
| Right Ascension (J2000) | 93.93735211° (6h 15.7m) |
| Declination (J2000) | 12.55107027° (+12° 33.1') |
| Galactic Longitude | 197.70757283° |
| Galactic Latitude | -2.04254960° |
| Proper motion RA | -1.51 mas/yr |
| Proper motion Dec | -1.43 mas/yr |
| Parallax | 2.34 ± 0.16 mas |
| Spectral Type | B9II-III |
| Radial Velocity | 12.90 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| U | 5.30 | -2.85 |
| B | 5.46 | -2.69 |
| V | 5.47 | -2.68 |
| J | 5.25 | -2.90 |
| H | 5.27 | -2.88 |
| K | 5.26 | -2.89 |
Colour index B-V: -0.00
Derivations
- Heliocentric distance: 426.80 pc (1,392 light years) (6.8% margin of error)
- Absolute visual magnitude: -2.68
- Transverse velocity: 4.2 km/s
- Space velocity relative to the Sun: 13.6 km/s
- Galactic position (X, Y, Z): -406.3 pc, -129.7 pc, -15.2 pc
- Galactic velocity (U, V, W): -11.8 km/s, -4.9 km/s, -4.5 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.