Phi-1 Orionis, a blue-white subgiant star in Orion
Phi-1 Orionis is a blue-white subgiant star in the constellation Orion. At 1,220 light years away, it shines at an apparent visual magnitude of 4.41.
Phi-1 Orionis (HIP 26176)
Phi-1 Orionis is a blue-white subgiant star in the constellation Orion. At 1,220 light years away, it shines at an apparent visual magnitude of 4.41. It is moving through the Galaxy at a speed of 33.9 km/s relative to the Sun.
Sky position: RA 5h 34.8m, Dec +9° 29.4'
Common designations: lambda Ori X-5, Phi-1 Orionis, 37 Orionis, HR 1876, HD 36822, Gaia DR3 3337904172766584064, HIP 26176
Phi-1 Orionis has the spectral type B0.2IV. 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 IV marks it as a subgiant: it has exhausted hydrogen in its core and is beginning to expand toward the giant phase.
How to find Phi-1 Orionis in the sky
Phi-1 Orionis lies in Orion. With a declination of +9° 29.4', it is visible from the entire Northern Hemisphere and from the Southern Hemisphere down to about latitude 81° 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 Phi-1 Orionis
Astrometry and spectroscopy
| Right Ascension (J2000) | 83.70515678° (5h 34.8m) |
| Declination (J2000) | 9.48958622° (+9° 29.4') |
| Galactic Longitude | 195.40225729° |
| Galactic Latitude | -12.28906112° |
| Proper motion RA | 2.96 mas/yr |
| Proper motion Dec | -2.46 mas/yr |
| Parallax | 2.67 ± 0.29 mas |
| Spectral Type | B0.2IV |
| Radial Velocity | 33.20 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| U | 3.29 | -4.57 |
| B | 4.26 | -3.60 |
| V | 4.41 | -3.45 |
| R | 4.42 | -3.44 |
| I | 4.59 | -3.27 |
| J | 4.81 | -3.06 |
| H | 4.85 | -3.01 |
| K | 4.86 | -3.01 |
Colour index B-V: -0.15
Derivations
- Heliocentric distance: 374.01 pc (1,220 light years) (10.7% margin of error)
- Absolute visual magnitude: -3.45
- Transverse velocity: 6.8 km/s
- Space velocity relative to the Sun: 33.9 km/s
- Galactic position (X, Y, Z): -352.3 pc, -97.1 pc, -79.6 pc
- Galactic velocity (U, V, W): -30.0 km/s, -14.9 km/s, -4.8 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.