Alpha Caeli, a yellow-white main-sequence star in Caelum
Alpha Caeli is a yellow-white main-sequence star in the constellation Caelum. At 66 light years away, it shines at an apparent visual magnitude of 4.45.
Alpha Caeli (HIP 21770)
Alpha Caeli is a yellow-white main-sequence star in the constellation Caelum. At 66 light years away, it shines at an apparent visual magnitude of 4.45. It is moving through the Galaxy at a speed of 15.4 km/s relative to the Sun.
Sky position: RA 4h 40.6m, Dec -41° 51.8'
Common designations: Alpha Caeli, HR 1502, HD 29875, GJ 174.1, GJ 174.1 A, GJ 9164, GJ 9164 A, HIP 21770
Alpha Caeli has the spectral type F2V. F-type stars are yellow-white stars of about 6,000 to 7,500 K, slightly hotter and more massive than the Sun. Their hydrogen lines are weaker than in A stars and metal lines become prominent. 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 Alpha Caeli in the sky
Alpha Caeli lies in Caelum. With a declination of -41° 51.8', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 48° N. Observers poleward of latitude 48° S see it as circumpolar: it never sets. It is bright enough to see with the naked eye under dark skies. It is highest in the sky at local midnight around December, which makes the weeks around that month the best time to observe it.
Tabulated data for Alpha Caeli
Astrometry and spectroscopy
| Right Ascension (J2000) | 70.14046881° (4h 40.6m) |
| Declination (J2000) | -41.86375126° (-41° 51.8') |
| Galactic Longitude | 246.15598920° |
| Galactic Latitude | -41.49576479° |
| Proper motion RA | -139.84 mas/yr |
| Proper motion Dec | -75.68 mas/yr |
| Parallax | 49.06 ± 0.09 mas |
| Spectral Type | F2V |
| Radial Velocity | 0.65 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| U | 4.79 | 3.24 |
| B | 4.79 | 3.24 |
| V | 4.45 | 2.90 |
| R | 4.11 | 2.56 |
| I | 3.90 | 2.35 |
| J | 3.94 | 2.40 |
| H | 3.65 | 2.11 |
| K | 3.72 | 2.18 |
Colour index B-V: +0.34
Derivations
- Heliocentric distance: 20.38 pc (66 light years) (0.2% margin of error)
- Absolute visual magnitude: 2.90
- Transverse velocity: 15.4 km/s
- Space velocity relative to the Sun: 15.4 km/s
- Galactic position (X, Y, Z): -6.2 pc, -14.0 pc, -13.5 pc
- Galactic velocity (U, V, W): 9.8 km/s, 5.0 km/s, -10.7 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.