Gamma Andromedae

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**Gamma Andromedae 1/2Aab/2B**
Observation data Epoch J2000
Image:GammaAndromedae.jpg Gamma Andromedae 1/2Aab/2B
Constellation (pronunciation)	Andromeda
Right ascension	02^h 03^m 54.0^s
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 (R_v)	-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 (M_V)	-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
Visual binary orbit
Companion	Gamma Andromedae 2B
Period (P)	60 yr
Semimajor axis (a)	9.7"
Visual binary orbit
Companion	Gamma Andromedae 2Aab
Period (P)	0.00739 yr
Semimajor axis (a)	0.5"
Other designations
Almach, Almaach, Almak, Alamak, 57 And, HR 603/604, BD +41°395, HD 12533/12534, SAO 37734/37735, FK5 73, GC 2477/2479, ADS 1630, CCDM 02039+4220, HIP 9640
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.

1 See also
2 Location
3 Position Stars
4 Components
5 References

[edit] See also

[edit] Location

The star's location is shown in the following chart Andromeda constellation:

Andromeda Constellation

[edit] Position Stars

Image:AlamakPosi1.jpg

Stars

[edit] Components

NAME	Right ascension	Declination	Apparent magnitude (V)	Spectral type	Database references
γ Andromedae B (ADS 1630 ABC)	02^h 03^m 54^s	+42° 19' 48	2.1		Simbad
γ Andromedae C (HD 12534)	02^h 03^m 54.75^s	+42° 19' 51.6	4.84	B8V+	Simbad
γ Andromedae D (BD+41 395C)	02^h 03^m 54.75^s	+42° 19' 51.6	8.3		Simbad

[edit] References

SIMBAD Query Result

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