Triple star system in the constellation Cassiopeia
YZ Cas Location of YZ Cassiopeiae (circled)
Observation dataEpoch J2000 Equinox J2000 Constellation Cassiopeia [ 1] A Right ascension 00h 45m 39.0777s [ 2] Declination +74° 59′ 17.063″[ 2] Apparent magnitude (V)5.653[ 3] B Right ascension 00h 45m 42,1503s [ 4] Declination +74° 58′ 43.242″[ 4] Apparent magnitude (V)11.23[ 5] Characteristics A Spectral type A2IV[ 6] [ 7] U−Bcolor index +0.07[ 5] B−Vcolor index +0.05[ 5] Variable type Algol [ 8] B Spectral type F2V[ 9] U−Bcolor index +0.64[ 5] B−Vcolor index +0.94[ 5] Astrometry Radial velocity (Rv )+8.90±0.4[ 10] km/s Proper motion (μ)RA: −15.07[ 2] mas /yr Dec.: −22.17[ 2] mas /yr Parallax (π)11.24± 0.55 mas [ 2] Distance 103.8[ 9] pc Absolute magnitude (MV )+0.251[ 7] Orbit [ 11] Companion TYC 4307-2168-1Period (P)86 580 yr Orbit [ 9] Primary Aa Companion Ab Period (P)4.467 days Semi-major axis (a)17.47 R ☉ [ 12] Eccentricity (e)0.0 Inclination (i)88.332° Details Aa Mass 2.308[ 12] M ☉ Radius 2.547[ 12] R ☉ Luminosity 41.69[ 12] L ☉ Surface gravity (log g )3.988[ 9] cgs Temperature 9,200[ 12] K Rotational velocity (v sin i )29.2[ 9] Ab Mass 1.325[ 13] M ☉ Radius 1.359[ 12] R ☉ Luminosity 3.34[ 12] L ☉ Surface gravity (log g )4.311[ 9] cgs Temperature 6,890[ 13] K Metallicity [Fe/H] +0.10[ 13] dex Rotational velocity (v sin i )15.0[ 9] Age 490 - 550[ 9] Myr Other designations 21 Cassiopeiae,HR 192,BD +74 27,HD 4161,SAO 4216,HIP 3572,GC 891,ADS 624 A,CCDM J00457+7459[ 14] Database references SIMBAD data
YZ Cassiopeiae (21 Cas) is astar system 103.8parsecs (339 ly ) away fromEarth , in the constellationCassiopeia . It comprises three stars: an eclipsingAlgol -type binary and a visually fainter star about 3000AU distant.[ 11] naked eye under good observing conditions.
Alight curve for YZ Cassiopeiae, plotted fromTESS [ 15] The primary star in the YZ Cassiopeiae system is a whitesubgiant (main sequence ) star ofspectral type A1Vm and 2.31 solar masses[ 11] M ☉ [ 3] M ☉ [ 11]
In 1924, Joel Stebbins announced his discovery that the star, then known as 21 Cassiopeiae, is aneclipsing binary .[ 16] variable star designation , YZ Cassiopeiae, in 1925.[ 17] apparent magnitude of the eclipsing binary varies from 5.65 to 6.05[ 3] [ 11] [ 11]
The binary has a dimmer (magnitude 9.7 according to Norton,[ 18] M ☉ [ 11] [ 11]
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