50 Cassiopeiae
Star in the constellation Cassiopeia
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50 Cassiopeiae, also named Gang,[9] 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.[10] 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]
  | |
| 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 | |
| Gang, 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.[12] 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.[13]
In Chinese astronomy, this star is part of the asterism Gàng (槓, "Shaft"), itself part of Huá Gài (華蓋 "Canopy of the Emperor"). The IAU Working Group on Star Names approved the name Gang for this star on 25 December 2025, and it is now so entered in the IAU Catalog of Star Names. The name Huagai was adopted for ι Cassiopeiae, and Custos (after Custos Messium) for BE Camelopardalis.[9]