Alpha Cassiopeiae
Alpha Cassiopeiae or α Cassiopeiae, also named Schedar (/ˈʃɛdɑːr/), is a second-magnitude star in the northern constellation of Cassiopeia. Though listed as the "alpha star" by Johann Bayer, α Cas's visual brightness closely matches the 'beta' (β) star in the constellation (Beta Cassiopeiae) and it may appear marginally brighter or dimmer, depending on which passband is used. However, recent calculations from NASA's WISE telescope confirm that α Cas is the brightest in Cassiopeia, with an apparent magnitude of 2.240. Its absolute magnitude is 18 times greater than β Cas, and it is located over four times farther away from the Sun.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 00h 40m 30.4411s |
| Declination | +56° 32′ 14.392″ |
| Apparent magnitude (V) | 2.240 |
| Characteristics | |
| Spectral type | K0-IIIa |
| U−B color index | 1.14 |
| B−V color index | 1.16 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | −4.31 km/s |
| Proper motion (μ) | RA: 50.88 mas/yr Dec.: −32.13 mas/yr |
| Parallax (π) | 14.29 ± 0.15 mas |
| Distance | 228 ± 2 ly (70.0 ± 0.7 pc) |
| Absolute magnitude (MV) | −2.01 |
| Details | |
| Mass | 3.98 M☉ |
| Radius | 45.39 R☉ |
| Luminosity | 794 L☉ |
| Surface gravity (log g) | 1.73 cgs |
| Temperature | 4,552 K |
| Metallicity [Fe/H] | –0.2 dex |
| Rotational velocity (v sin i) | 6.71 km/s |
| Age | 220 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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