Eta Cassiopeiae

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**Eta Cassiopeiae A/B**
Observation data Epoch J2000
Constellation	Cassiopeia
Right ascension	00h 49m 06.3s
Declination	+57° 48' 54"
Apparent magnitude (V)	3.46/7.51
Spectral Characteristics
Spectral type	G3V/K7V
U-B color index	0.02/1.03
B-V color index	0.57/1.39
Variable type	RS CVn
Astrometry
Radial velocity (R_v)	+8.5 km/s
Proper motion (μ)	RA: 1087.11 mas/yr Dec.: -0559.65 mas/yr
Parallax (π)	168.38 ± 0.59 mas
Distance	19.37 ± 0.07 ly (5.94 ± 0.02 pc)
Absolute magnitude (M_V)	4.59/8.64
Visual binary orbit
Companion	Gl 34B
Period (P)	480 years
Semimajor axis (a)	11.99"
Eccentricity (e)	0.497
Inclination (i)	34.76°
Node (Ω)	98.42°
Periastron epoch (T)	88.59
Physical Characteristics
Mass	0.91/0.56 M_☉
Radius	1,17/0.40 R_☉
Luminosity	1.20/0.03 L_☉
Temperature	5600/3800 K
Metallicity	63-68%
Rotation	?
Age	? years
Other designations
Achird, 24 Cassiopeiae, GJ 34, HR 219, BD+57°150, HD 4614, GCTP 155, LHS 123/122, LFT 74, LTT 10287, SAO 21732, Wolf 24, Struve 60, HIP 3821, GC 962, ADS 671, CCDM J00491+5749

Eta Cassiopeiae (η Cas / η Cassiopeiae) is a star system 19.4 light years away from Earth, in the constellation Cassiopeia. Sometimes the traditional name Achird is used. It is known as 王良三 (the Third Star of Wang Liang) in Chinese.

The primary star in the η Cassiopeiae system is a yellow dwarf (main sequence) star of spectral type G3V, putting it in the same spectral class as our Sun, which is of spectral type G2V. It therefore resembles what our Sun might look like if we were to observe it from η Cassiopeiae. The star is of apparent magnitude 3.45. The star has a cooler and dimmer (magnitude 7.51) orange dwarf companion of spectral type K7V. The system is an RS Canum Venaticorum type variable star and its brightness varies by 0.05 magnitudes.

There are six dimmer optical components listed in the Washington Double Star Catalog. However, none of them are related to the η Cassiopeiae system and are in reality more distant stars.