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ι Cassiopeiae
	; The Bayer-designated stars in Cassiopeia. Iota Cassiopeiae is circled.
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Cassiopeia
	ι Cas A
Right ascension	02h 29m 03.960s
Declination	+67° 24′ 08.70″
Apparent magnitude (V)	4.61 (4.65 / 8.48)
	ι Cas B
Right ascension	02h 29m 03.567s
Declination	+67° 24′ 07.01″
Apparent magnitude (V)	6.87
	ι Cas C
Right ascension	02h 29m 05.086s
Declination	+67° 24′ 05.53″
Apparent magnitude (V)	9.05 (9.14 / 11.84)
Characteristics
U−B color index	+0.03
B−V color index	+0.12
ι Cas A
Spectral type	A3p / G6
Variable type	α2 CVn
ι Cas B
Spectral type	F5
ι Cas C
Spectral type	K4 / M2
U−B color index	+0.18
B−V color index	+0.72
Astrometry
Radial velocity (Rv)	1.2 ± 2 km/s
Proper motion (μ)	RA: -26.61 mas/yr ; Dec.: 38.21 mas/yr
Parallax (π)	22.22 ± 0.08 mas
Distance	146.8 ± 0.5 ly ; (45.0 ± 0.2 pc)
Absolute magnitude (MV)	1.62 ± 0.07 (Aa); 5.60 ± 0.17 (Ab)
Orbit
Primary	ι Cas Aa
Companion	ι Cas Ab
Period (P)	48.72 ± 0.45 yr
Semi-major axis (a)	0.423 ± 0.004″
Eccentricity (e)	0.637 ± 0.004
Inclination (i)	148.2 ± 1.3°
Longitude of the node (Ω)	176.6 ± 1.8°
Periastron epoch (T)	B 1993.21 ± 0.05
Argument of periastron (ω); (secondary)	328.2 ± 1.9°
Orbit
Primary	ι Cas A
Companion	ι Cas B
Period (P)	2400 yr
Semi-major axis (a)	6.50″
Eccentricity (e)	0.40
Inclination (i)	102.9 ± 0.3°
Longitude of the node (Ω)	188.0 ± 0.9°
Periastron epoch (T)	B 940 ± 47
Argument of periastron (ω); (secondary)	113.3 ± 3.4°
Details
ι Cas Aa
Mass	1.98 M☉
Radius	2.3 ± 0.4 R☉
Luminosity	24 L☉
Temperature	8360 ± 275 K
Rotation	1.74033 d
Rotational velocity (v sin i)	48 km/s
Age	100 Myr
ι Cas Ab
Mass	0.98 M☉
ι Cas B
Mass	1.28 M☉
Temperature	6540 K
ι Cas Ca
Temperature	4520 ± 20 K
ι Cas Cb
Temperature	3590 ± 45 K
Other designations
	BD+66° 213, HD 15089, HIP 11569, HR 707, SAO 12298
	ι Cas A: TYC 4058-1504-1
	ι Cas B: TYC 4058-1504-2
	ι Cas C: TYC 4058-1505-1
Database references
	ι Cas AB
	ι Cas A
	ι Cas B
	ι Cas C

Iota Cassiopeiae (ι Cas, ι Cassiopeiae) is a star system in the constellation Cassiopeia. The system has a combined apparent magnitude of 4.53,^{[citation needed]} making it visible to the naked eye. Based on its parallax, it is located about 133 light-years (41 parsecs) from Earth.^[7]

Components

A light curve for Iota Cassiopeiae, plotted from *TESS* data^[11]

Iota Cassiopeiae is known to be a quintuple star system. The brightest star system, ι Cassiopeiae A, contains a white-colored A-type main-sequence star with a mean apparent magnitude of +4.61.^[1] The primary is itself a tighter binary star system. The two stars were resolved by adaptive optics.^{[citation needed]} These are designated Aa and Ab (although confusingly they may also be labeled as A and Aa, respectively).^{[citation needed]} The primary is classified as an Alpha² Canum Venaticorum-type variable star and the brightness of the system varies from magnitude +4.45 to +4.53 with a period of 1.74 days,^[5] because of its magnetic field.^[10] The variability in brightness was first detected by Karl D. Rakos in 1962, although its spectrum was known to be variable from earlier observations.^[12] The fainter companion is a G-type star with a mass of 0.98 M_☉.^[8] The orbital period of the system is about 49 years.^[8]

ι Cassiopeiae B is a yellow-white F-type main sequence dwarf with an apparent magnitude of +6.87.^[1] It orbits around ι Cassiopeiae A approximately every 2,400 years with a semi-major axis of around 6.5 arcseconds, but the orbit is not very well constrained.^[8] This object may be causing Kozai–Lidov cycles in the inner orbital pair.^[8]

ι Cassiopeiae C is itself another binary, designated Ca and Cb,^[8] or just C and c.^[3] It comprises two stars, a K-type star and an M-type star.^[3] It is currently at an angular distance of about 7 arcseconds from the AB pair.^[13] Since the semimajor axis of the AB orbit is about 6.5 arcseconds, the true semimajor axis of C's orbit around them is thought to be significantly larger than 7 arcseconds.^[8]