Alpha Horologii
Star in the constellation Horologium
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Alpha Horologii (α Horologii) is a solitary[10] orange-hued giant star and the brightest star in the constellation Horologium. It is visible to the naked eye with an apparent visual magnitude of +3.85.[2] Based upon an parallax shift of 27.721 mas as seen from the Earth, it is located at a distance of 117.6 light-years (36.1 parsecs).[1] The star is moving away from the Sun with a radial velocity of +21.6 km/s.[5]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Horologium |
| Right ascension | 04h 14m 00.114s[1] |
| Declination | −42° 17′ 39.73″[1] |
| Apparent magnitude (V) | +3.846[2] |
| Characteristics | |
| Evolutionary stage | Giant star |
| Spectral type | K2 III[3] |
| U−B color index | +1.013[4] |
| B−V color index | 1.083±0.037[2] |
| Astrometry | |
| Radial velocity (Rv) | +21.6±0.3[5] km/s |
| Proper motion (μ) | RA: +41.992±0.125 mas/yr[1] Dec.: −203.157±0.154 mas/yr[1] |
| Parallax (π) | 27.721±0.11195 mas[1] |
| Distance | 117.6+0.55 −0.52 ly (36.06+0.17 −0.16 pc)[6] |
| Absolute bolometric magnitude (Mbol) | +1.08[7] |
| Details[2] | |
| Mass | 1.409±0.265 M☉ |
| Radius | 9.931±0.351 R☉ |
| Luminosity | 37.61[8] L☉ |
| Surface gravity (log g) | 2.82±0.02 cgs |
| Temperature | 4695±50 K |
| Metallicity [Fe/H] | −0.03±0.03 dex |
| Age | 3.561±2.333 Gyr |
| Other designations | |
| α Hor, CD−42°1425, HD 26967, HIP 19747, HR 1326, SAO 216710[9] | |
| Database references | |
| SIMBAD | data |
The stellar classification of K2 III[3] indicates this is an evolved giant star of the K class. This means it has consumed the hydrogen at its core and has migrated away from the main sequence, with its outer envelope cooling and expanding in the process. Alpha Horologii has an estimated 1.41 times the mass of the Sun[2] and is radiating 38[8] times the Sun's luminosity from its photosphere at an effective temperature of 4,695 K.[2] Being 3.56 billion years old, it has swollen to around 10 times the diameter of the Sun,[2] having spent much of its life as a white main sequence star.[11]