2 Cassiopeiae
Star in the constellation Cassiopeia
From Wikipedia, the free encyclopedia
2 Cassiopeiae (2 Cas) is a white bright giant in the constellation Cassiopeia, about 2,800 light years away. It is a chemically peculiar Am star.
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Cassiopeia[1] |
| Right ascension | 23h 09m 44.1389s[2] |
| Declination | +59° 19′ 57.687″[2] |
| Apparent magnitude (V) | +5.679[3] |
| Characteristics | |
| Spectral type | A4II[4] (kA5hA7mF0)[5] |
| U−B color index | +0.31[6] |
| B−V color index | +0.33[6] |
| Astrometry | |
| Radial velocity (Rv) | −13.58±0.15[2] km/s |
| Proper motion (μ) | RA: +0.335[2] mas/yr Dec.: +0.552[2] mas/yr |
| Parallax (π) | 1.1900±0.0386 mas[2] |
| Distance | 2,740 ± 90 ly (840 ± 30 pc) |
| Absolute magnitude (MV) | −2.92[1] |
| Details | |
| Mass | 5.3[7] M☉ |
| Radius | 41[8] R☉ |
| Luminosity | 3,014[8] L☉ |
| Surface gravity (log g) | 1.93[7] cgs |
| Temperature | 8,012[9] K |
| Metallicity [Fe/H] | −0.23[7] dex |
| Rotational velocity (v sin i) | 5.3[10] km/s |
| Age | 174[11] Myr |
| Other designations | |
| 2 Cas, HR 8822, HD 218753, BD+58°2552, HIP 114365 | |
| Database references | |
| SIMBAD | data |
2 Cassiopeiae has been described as an A4 type bright giant, but its spectrum is not easy to classify. The calcium K absorption lines indicate a hotter type than the hydrogen lines, while other metals indicate a cooler type, possibly as cool as F0. This makes it an Am star, a type of magnetic chemically peculiar star with unusual abundances showing in its spectrum due to chemical stratification in its atmosphere caused by slow rotation.[6]
About six times as massive as the Sun and 3,000 times as luminous, it has expanded away from the main sequence after exhausting its core hydrogen and now has an effective temperature of about 8,000 K. Some researchers have suggested that it is a post-AGB star.[4]
2 Cassiopeiae has a number of close companions listed in multiple star catalogues,[12] but none are thought to be gravitationally associated.[13]