WZ Cassiopeiae
Star in the constellation Cassiopeia
From Wikipedia, the free encyclopedia
WZ Cassiopeiae (WZ Cas) is a deep red hued star in the northern constellation of Cassiopeia. It is a variable star with a magnitude that ranges from 6.3 down to 8.8,[3] placing it near the limit of naked eye visibility at peak magnitude. The estimated distance to this star, as determined from its annual parallax shift of 2.1 mas,[2] is about 1,540 light years. It is moving closer to the Earth with a heliocentric radial velocity of −34 km/s.[7]
 WZ Cassiopeiae in optical light | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia[1] |
| Right ascension | 00h 01m 15.85680s[2] |
| Declination | +60° 21′ 19.0259″[2] |
| Apparent magnitude (V) | 6.3 – 8.8[3] |
| Characteristics | |
| Evolutionary stage | AGB[4] |
| Spectral type | C-N7 III: C2 2 Li 10[5] |
| U−B color index | +4.29[6] |
| B−V color index | +2.835±0.040[1] |
| Variable type | SRb[3] |
| Astrometry | |
| Radial velocity (Rv) | −34.0±2[7] km/s |
| Proper motion (μ) | RA: +10.7693[2] mas/yr Dec.: −5.672[2] mas/yr |
| Parallax (π) | 2.1227±0.0297 mas[2] |
| Distance | 1,540 ± 20 ly (471 ± 7 pc) |
| Details | |
| Mass | 5.2[8] M☉ |
| Radius | ~600[9] R☉ |
| Luminosity | 12,400[10] L☉ |
| Surface gravity (log g) | 1.55[8] cgs |
| Temperature | 3,095[10] K |
| Metallicity [Fe/H] | −0.19[8] dex |
| Other designations | |
| WZ Cas, BD+59°2810, HD 224855, HIP 99, SAO 21002[11] | |
| Database references | |
| SIMBAD | data |
João de Moraes Pereira discovered that the star's brightness varies, in 1893. It was given its variable star designation in 1921.[12] This is a semiregular variable of subtype SRb[3] with periods of 186 and 366 days due to radial pulsations.[9]
This is an aging carbon star on the asymptotic giant branch.[9] Keenan (1993) assigned it a classification of C-N7 III: C2 2 Li 10, which indicates it is of the N star subtype in the revised Morgan–Keenan system, with a C2 strength index of 2 (a measure of the excess of carbon over oxygen) and an anomalously strong line of lithium at 6707 Å.[5] It is losing mass at the rate of 6.5×10−9 M☉ yr−1, which is on the low side for a star of this type. It has expanded to around 600 times the Sun's radius and is radiating 12,400 times the Sun's luminosity[10] from its photosphere at a relatively cool[13] effective temperature of 3,095 K.[10]
A magnitude 8.4 B-type visual companion, designated HD 224869, is located at an angular separation of 58″. The difference in the radial velocities for the two stars – 20 km/s – is too large for them to be dynamically associated.[14]