Hamal
 Location of Hamal (α Arietis) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Aries |
| Right ascension | 02h 07m 10.40570s |
| Declination | +23° 27′ 44.7032″ |
| Apparent magnitude (V) | 2.00 |
| Characteristics | |
| Spectral type | K1IIIb |
| U−B color index | +1.13 |
| B−V color index | +1.15 |
| V−R color index | +0.7 |
| R−I color index | +0.62 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | −14.2 ± 0.9 km/s |
| Proper motion (μ) |
RA: +188.55 mas/yr Dec.: −148.08 mas/yr |
| Parallax (π) | 49.56 ± 0.25mas |
| Distance | 65.8 ± 0.3 ly (20.2 ± 0.1 pc) |
| Absolute magnitude (MV) | +0.47 ± 0.04 |
| Details | |
| Mass | 1.5 ± 0.2 M☉ |
| Radius | 14.9 ± 0.3 R☉ |
| Luminosity (bolometric) | 91 ± 6 L☉ |
| Surface gravity (log g) | 2.57 cgs |
| Temperature | 4,480 K |
| Metallicity [Fe/H] | –0.25 dex |
| Rotational velocity (v sin i) | 3.44 km/s |
| Age | 3.4 ± 1.9 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Hamal, alternatively designated Alpha Arietis (α Arietis, abbreviated Alpha Ari, α Ari), is the brightest star in the northern zodiacal constellation of Aries.
With an apparent visual magnitude of 2.0, it is among the brightest stars in the night sky. Based upon parallax measurements made with the Hipparcos astrometry satellite, Hamal is about 65.8 light-years (20.2 parsecs) from Earth. It is a giant star that may host an orbiting planet with a mass greater than Jupiter.
Alpha Arietis is the star's Bayer designation. It also bears the Flamsteed designation of 13 Arietis.
The traditional name Hamal (also written Hemal, Hamul, Ras Hammel) derives from the Arabic راس الحمل rās al-ħamal "head of the ram", in turn from the name for the constellation as a whole, Al Ħamal "the ram". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Hamal for this star.
In Chinese, 婁宿 (Lóu Su), meaning Bond (asterism), refers to an asterism consisting of Hamal, β Arietis and γ Arietis. Consequently, Hamal itself is known as 婁宿三 (Lóu Su sān, English: the Third Star of Bond.)
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