Gamma Andromedae
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| Observation data 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 | ? years |
| 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). It is 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.
[edit] See also
[edit] Location
The star's location is shown in the following chart Andromeda constellation:
[edit] References
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