50 Cassiopeiae

50 Cassiopeiae is a white star in the northern constellation of Cassiopeia. In the past, it had been misidentified as a suspected nebula, and given the number NGC 771.^[9] The star is visible to the naked eye, having an apparent visual magnitude of +3.95.^[1] Based upon an annual parallax shift of 20.76 mas, it is located 157 light years away. It is moving closer, having a heliocentric radial velocity of −18 km/s,^[4] and will approach to within 82 ly in 1.879 million years.^[1]

A light curve for 50 Cassiopeiae, plotted from TESS data^[10]

50 Cassiopeiae

50 Cassiopeiae in optical light
Observation data Epoch J2000      Equinox J2000
Constellation	Cassiopeia[1]
Right ascension	02h 03m 26.10206s[2]
Declination	+72° 25′ 16.6376″[2]
Apparent magnitude (V)	+3.95[1]
Characteristics
Evolutionary stage	main sequence[3]
Spectral type	A2 V[3]
B−V color index	−0.002±0.007[1]
Astrometry
Radial velocity (Rv)	−18.2±0.9[4] km/s
Proper motion (μ)	RA: −43.57[5] mas/yr Dec.: +22.30[5] mas/yr
Parallax (π)	20.76±0.14 mas[5]
Distance	157 ± 1 ly (48.2 ± 0.3 pc)
Absolute magnitude (MV)	0.54[1]
Details
Mass	2.56±0.03[3] M☉
Radius	2.5[6] R☉
Luminosity	63.8+3.5 −6.4[3] L☉
Temperature	9,376+240 −235[3] K
Metallicity [Fe/H]	+0.18±0.28[7] dex
Rotational velocity (v sin i)	91[3] km/s
Other designations
50 Cas, BD+71°117, FK5 70, GC 2445, HD 12216, HIP 9598, HR 580, SAO 4560, NGC 771[8]
Database references
SIMBAD	data

It is an A-type main-sequence star with a stellar classification of A2 V.^[3] It is a suspected variable star with a very small amplitude.^[11] 50 Cas has an estimated 2.56 times the mass of the Sun,^[3] and about 2.5 times the Sun's radius.^[6] It is radiating 64 times the Sun's luminosity from its photosphere at an effective temperature of around 9,376 K.^[3]

The star was the brightest star in the occasionally used 1775 to 19th century constellation Custos Messium, typically drawn as a depiction of Charles Messier standing on top of the giraffe (Camelopardalis), between Cepheus and Cassiopeia.^[12]