21 Canum Venaticorum is a single[9] variable star[5] in the northern constellation of Canes Venatici, located 277 light years away from the Sun.[1] This object has the variable star designation BK Canum Venaticorum; 21 Canum Venaticorum is the Flamsteed designation. It is visible to the naked eye as a faint white-hued star with a baseline apparent visual magnitude of +5.14.[2]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Canes Venatici |
Right ascension | 13h 18m 14.50967s[1] |
Declination | +49° 40′ 55.4245″[1] |
Apparent magnitude (V) | +5.14[2] |
Characteristics | |
Spectral type | B9 IV (Si)[3] or A0 V Si:[4] |
B−V color index | −0.049±0.002[2] |
Variable type | α2 CVn[5] |
Astrometry | |
Radial velocity (Rv) | −2.9±2.8[2] km/s |
Proper motion (μ) | RA: −35.235[1] mas/yr Dec.: +16.655[1] mas/yr |
Parallax (π) | 11.7559 ± 0.1344 mas[1] |
Distance | 277 ± 3 ly (85.1 ± 1.0 pc) |
Absolute magnitude (MV) | 0.48[6] |
Details | |
Mass | 2.73[7] M☉ |
Radius | 2.8±0.3[6] R☉ |
Luminosity | 72.49[2] L☉ |
Surface gravity (log g) | 4.05[7] cgs |
Temperature | 11,036±375[7] K |
Rotational velocity (v sin i) | 96[7] km/s |
Age | 201[7] Myr |
Other designations | |
Database references | |
SIMBAD | data |
According to Garrison et al. (1994)[3] this is a B-type subgiant star with a stellar classification of B9 IV (Si), where the suffix notation indicates this is a Silicon star. Cowley et al. (1969) listed it with a class of A0 V Si:,[4] which would match an A-type main-sequence star with the ':' indicating some uncertainty in the classification. It is a marginally chemically-peculiar star[10] with weaker than normal helium absorption lines and displaying helium line variability.[11] The widths of the lines of ionized silicon vary with a period of 21.12 ± 0.48 hours.[12]
21 Canum Venaticorum is classified as an Alpha2 Canum Venaticorum type variable star and its brightness varies by 0.04 magnitudes over a period of 18.4 hours.[5] It is around 201 million years old and is spinning with a relatively high projected rotational velocity of 96 km/s.[7] The star has 2.73[7] times the mass of the Sun and 2.8[6] times the Sun's radius. It is radiating 72[2] times the luminosity of the Sun from its photosphere at an effective temperature of 11,036 K.[7]