Lambda Cassiopeiae

Lambda Cassiopeiae is a binary star system in the northern constellation of Cassiopeia. Its name is a Bayer designation that is Latinized from λ Cassiopeiae, and abbreviated Lambda Cas or λ Cas. The system has a combined apparent magnitude of +4.74, making it faintly visible to the naked eye. With an annual parallax shift of 8.64 mas,^[2] it is approximately 380 light years from Earth. The system is moving closer to the Sun with a radial velocity of −12 km/s.^[6]

λ Cassiopeiae in optical light

λ Cassiopeiae

Location of λ Cassiopeiae (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cassiopeia[1]
Right ascension	00h 31m 46.35935s[2]
Declination	+54° 31′ 20.2257″[2]
Apparent magnitude (V)	4.772[3] (5.33 / 5.62)[4]
Characteristics
Spectral type	B8 Vnn[1]
U−B color index	−0.35[5]
B−V color index	−0.10[5]
Astrometry
Radial velocity (Rv)	−12.20±1.3[6] km/s
Proper motion (μ)	RA: +41.20±0.29[2] mas/yr[2] Dec.: −16.54±0.35 mas/yr[2]
Parallax (π)	8.64±0.43 mas[2]
Distance	380 ± 20 ly (116 ± 6 pc)
Absolute magnitude (MV)	−0.57[1]
Orbit[4]
Period (P)	245.70±35.96 yr
Semi-major axis (a)	0.448±0.028″
Eccentricity (e)	0.689±0.119
Inclination (i)	53.6±5.2°
Longitude of the node (Ω)	17.6±9.6°
Periastron epoch (T)	2025.54±4.56
Argument of periastron (ω) (secondary)	301.0±2.6°
Details
λ Cas A
Mass	2.9+0.45 −0.40[7] M☉
Radius	3.50[8] R☉
Luminosity	255[1] L☉
Surface gravity (log g)	4.0±0.25[7] cgs
Temperature	12,000±1,000[7] K
Rotational velocity (v sin i)	253[9] km/s
Age	58+104 −48[7] Myr
Other designations
λ Cas, 14 Cassiopeiae, BD+53°82, HD 2772, HIP 2505, HR 123, SAO 21489, ADS 434, CCDM J00318+5431, WDS J00318+5431AB[10]
Database references
SIMBAD	λ Cas
	λ Cas A
	λ Cas B

Both components are blue-white B-type main-sequence stars. The brighter member, component A, has an apparent magnitude of +5.5, while its companion, component B, has an apparent magnitude of +5.8. The two stars are separated by 0.6 arcseconds and complete one orbit around their common centre of mass about once every 250 years.^[4] The primary displays an infrared excess, possibly due to a debris disk or other orbiting material.^[8]