Gamma Andromedae
File:GammaAndromedae.jpg Gamma Andromedae 1/2Aab/2B | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 02h 03m 54.0s |
| Declination | +42° 19′ 47″ |
| Apparent magnitude (V) | 2.10/5.1/6.3 |
| Characteristics | |
| Spectral type | K3 IIb/B8 V/A0 V |
| U−B color index | 1.58/-0.12 |
| B−V color index | 1.37/0.03 |
| Variable type | ? |
| Astrometry | |
| Radial velocity (Rv) | -12 km/s |
| Proper motion (μ) | RA: 43.08 mas/yr Dec.: -50.85 mas/yr |
| Parallax (π) | 9.19 ± 0.73 mas |
| Distance | 350 ± 30 ly (109 ± 9 pc) |
| Absolute magnitude (MV) | -3.09/-0.1/1.1 |
| Details | |
| Mass | ? M☉ |
| Radius | 73.5 R☉ |
| Luminosity | 2,000 L☉ |
| Temperature | 4,500/10,000/10,000 K |
| Metallicity | ? |
| Rotation | <14/70 km/s. |
| Age | 1.5 billion years |
| Orbit | |
| Companion | Gamma Andromedae 2B |
| Period (P) | 60 yr |
| Semi-major axis (a) | 9.7″ |
| Orbit | |
| Companion | Gamma Andromedae 2Aab |
| Period (P) | 0.00739 yr |
| Semi-major axis (a) | 0.5″ |
| Other designations | |
| Database references | |
| SIMBAD | data |
Gamma Andromedae (γ And / γ Andromedae) is a four star system in the constellation Andromeda. It is also known by the traditional name Almach (also written as Almaach, Almaack, Almak, Alamak), alledgedly from the Arabic al-canāq al-arđ̧ the "earth-kid" (a mustelid). It was known as 天大將軍一 (the First Star of the Great General of the Heaven) in Chinese.
In small telescopes, γ Andromedae can be easily resolved as a double star, and is said to be a very interesting and beautiful sight for amateur astronomers. The main star (γ1) is a magnitude +2.13 orange bright giant (spectral type K3 IIb). The companion (γ2) with a magnitude of +4.84 is 9.6 arc seconds away at a position angle of 63 degrees.
Interestingly, γ2 itself can be resolved as a double star with much larger telescopes. Its two components are a B8 main sequence dwarf (magnitude +5.1), and an A0 dwarf (magnitude +6.3). They have an orbital period of 61 years. The brighter of these is known to be a spectroscopic binary itself, with an orbital period of 2.67 days. Thus γ2 is a triple star.
See also
Location
The star's location is shown in the following chart Andromeda constellation:
Position Stars
Components
| NAME | Right ascension | Declination | Apparent magnitude (V) | Spectral type | Database references |
|---|---|---|---|---|---|
| γ Andromedae B (ADS 1630 ABC) | 02h 03m 54s | +42° 19' 48 | 2.1 | Simbad | |
| γ Andromedae C (HD 12534) | 02h 03m 54.75s | +42° 19' 51.6 | 4.84 | B8V+ | Simbad |
| γ Andromedae D (BD+41 395C) | 02h 03m 54.75s | +42° 19' 51.6 | 8.3 | Simbad |
References
- http://www.alcyone.de/cgi-bin/search.pl?object=HR0603
- http://www.freewebs.com/starsurf/constellations/andromeda.htm
- http://www.daviddarling.info/encyclopedia/A/Almaak.html
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