Alpha Cassiopeiae

Schedar, α Cas

Shedar is the star labelled α at the bottom right of the "W"
Observation data Epoch J2000      Equinox J2000
Constellation	Cassiopeia
Right ascension	00h 40m 30.4405s
Declination	+56° 32′ 14.392″
Apparent magnitude (V)	2.240
Characteristics
Spectral type	K0IIIa
U−B color index	1.14
B−V color index	1.16
Variable type	Suspected
Astrometry
Radial velocity (Rv)	−4.31 km/s
Proper motion (μ)	RA: 50.36 mas/yr Dec.: −32.17 mas/yr
Parallax (π)	14.29 ± 0.15mas
Distance	228 ± 2 ly (70.0 ± 0.7 pc)
Absolute magnitude (MV)	−1.985
Details
Mass	4–5 M☉
Radius	42.1 ± 1.7 R☉
Luminosity	676 L☉
Temperature	4,530 K
Metallicity [Fe/H]	–0.1 dex
Rotational velocity (v sin i)	21 km/s
Age	1–2×108 years
Other designations
Schedar, α Cas, 18 Cas, HR 168, BD+55°139, HD 3712, SAO 21609, FK5 21, HIP 3179, GC 792, ADS 561, CCDM J00405+5632
Database references
SIMBAD	data

Coordinates: 00^h 40^m 30.5^s, +56° 32′ 14.5″

Alpha Cassiopeiae (α Cassiopeiae, abbreviated Alpha Cas, α Cas), also named Schedar, is a second magnitude star in the constellation of Cassiopeia. Though listed as the "alpha star" by Johann Bayer, α Cas's visual brightness closely rivals the 'beta' (β) star in the constellation (Beta Cassiopeiae, also named Caph) and it may appear marginally brighter or dimmer, depending on which passband is used. However, recent calculations from NASA's WISE telescope confirm that α Cas is the brightest in Cassiopeia, with a apparent magnitude of 2.240. Its absolute magnitude is 18 times greater than β Cas, although it is located farther away from the Sun (228 light years versus 54).

α Cassiopeiae (Latinised to Alpha Cassiopeiae) is the star's Bayer designation.