Upsilon1 Cassiopeiae
Star in the constellation Cassiopeia
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Upsilon1 Cassiopeiae is an astrometric binary[11] star system in the northern constellation of Cassiopeia. Its name is a Bayer designation that is Latinized from υ1 Cassiopeiae, and abbreviated Upsilon1 Cas or υ1 Cas. This system visible to the naked eye with an apparent visual magnitude of 4.82.[3] Based upon an annual parallax shift of 9.93 mas as seen from Earth,[2] this system is located about 330 light years from the Sun. It is drifting closer to the Sun with a radial velocity of −24 km/s.[6]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cassiopeia[1] |
| Right ascension | 00h 55m 00.156s[2] |
| Declination | +58° 58′ 21.72″[2] |
| Apparent magnitude (V) | 4.82[3] |
| Characteristics | |
| Evolutionary stage | red clump[4] |
| Spectral type | K2 III[5] |
| U−B color index | +1.25[3] |
| B−V color index | +1.21[3] |
| Astrometry | |
| Radial velocity (Rv) | −23.57[6] km/s |
| Proper motion (μ) | RA: −31.200 mas/yr[2] Dec.: −44.986 mas/yr[2] |
| Parallax (π) | 9.062±0.107 mas[2] |
| Distance | 360 ± 4 ly (110 ± 1 pc) |
| Absolute magnitude (MV) | −0.644[6] |
| Details | |
| Mass | 1.39[7] M☉ |
| Radius | 21[8] R☉ |
| Luminosity | 174[7] L☉ |
| Surface gravity (log g) | 1.76[6] cgs |
| Temperature | 4,422±14[7] K |
| Metallicity [Fe/H] | −0.25[6] dex |
| Rotational velocity (v sin i) | 1.1[9] km/s |
| Age | 4.75[7] Gyr |
| Other designations | |
| υ1 Cas, 26 Cas, BD+58°134, HD 5234, HIP 4292, HR 253, SAO 21832, ADS 748, CCDM J00551+5858, WDS J00550+5858A[10] | |
| Database references | |
| SIMBAD | data |
The visible component is an evolved K-type giant star with a stellar classification of K2 III.[5] With an estimated age of 4.75 billion years,[7] it is a red clump star that is generating energy through the fusion of helium at its core.[4] The measured angular diameter, after correction for limb darkening, is 1.97±0.02 mas.[12] At the estimated distance of the star, this yields a physical size of about 21 times the radius of the Sun.[8] It has 1.39 times the mass of the Sun and is radiating 174 times the Sun's luminosity from its expanded photosphere at an effective temperature of 4,422 K.[7]
There is a magnitude 12.50 visual companion at an angular separation of 17.80 arc seconds along a position angle of 61°, as of 2003. A more distant magnitude 12.89 companion lies at a separation of 93.30 arc seconds along a position angle of 125°, as measured in 2003. Neither star appears to be physically associated with υ1 Cas.[13]
