25 Orionis, a blue-white main-sequence star in Orion
25 Orionis is a blue-white main-sequence star in the constellation Orion. At 1,112 light years away, it shines at an apparent visual magnitude of 4.96.
25 Orionis (HIP 25302)
25 Orionis is a blue-white main-sequence star in the constellation Orion. At 1,112 light years away, it shines at an apparent visual magnitude of 4.96. It is moving through the Galaxy at a speed of 19.4 km/s relative to the Sun.
Sky position: RA 5h 24.7m, Dec +1° 50.8'
Common designations: Psi-1 Orionis, 25 Orionis, V1086 Orionis, HR 1789, HD 35439, HIP 25302, Gaia DR3 3222282691086558464
25 Orionis has the spectral type B1Vn. 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 V means it is a main-sequence (dwarf) star, still fusing hydrogen into helium in its core like the Sun.
How to find 25 Orionis in the sky
25 Orionis lies in Orion. With a declination of +1° 50.8', it is visible from the entire Northern Hemisphere and from the Southern Hemisphere down to about latitude 88° 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 25 Orionis
Astrometry and spectroscopy
| Right Ascension (J2000) | 81.18678077° (5h 24.7m) |
| Declination (J2000) | 1.84644498° (+1° 50.8') |
| Galactic Longitude | 200.95805122° |
| Galactic Latitude | -18.28918387° |
| Proper motion RA | 1.05 mas/yr |
| Proper motion Dec | 0.43 mas/yr |
| Parallax | 2.93 ± 0.12 mas |
| Spectral Type | B1Vn |
| Radial Velocity | 19.30 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| U | 3.83 | -3.83 |
| B | 4.76 | -2.90 |
| V | 4.96 | -2.70 |
| R | 5.04 | -2.62 |
| I | 5.26 | -2.40 |
| J | 5.37 | -2.30 |
| H | 5.42 | -2.25 |
| K | 5.36 | -2.31 |
Colour index B-V: -0.20
Derivations
- Heliocentric distance: 341.05 pc (1,112 light years) (4.2% margin of error)
- Absolute visual magnitude: -2.70
- Transverse velocity: 1.8 km/s
- Space velocity relative to the Sun: 19.4 km/s
- Galactic position (X, Y, Z): -302.4 pc, -115.8 pc, -107.0 pc
- Galactic velocity (U, V, W): -17.6 km/s, -7.0 km/s, -4.3 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.