| 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] orA0 V Si:[4] |
| B−Vcolor 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 | |
| 21 CVn,BK Canum Venaticorum,BD+50°1994,FK5 3063,HD 115735,HIP 64906,HR 5023,SAO 44556[8] | |
| Database references | |
| SIMBAD | data |
21 Canum Venaticorum is a single[9]variable star[5] in the northernconstellation ofCanes Venatici, located 277 light years away from the Sun.[1] This object has thevariable star designationBK Canum Venaticorum;21 Canum Venaticorum is theFlamsteed designation. It is visible to thenaked eye as a faint white-hued star with a baselineapparent visual magnitude of +5.14.[2]
According to Garrison et al. (1994)[3] this is aB-typesubgiant star with astellar classification ofB9 IV (Si), where the suffix notation indicates this is aSilicon star. Cowley et al. (1969) listed it with a class ofA0 V Si:,[4] which would match anA-type main-sequence star with the ':' indicating some uncertainty in the classification. It is a marginallychemically-peculiar star[10] with weaker than normal heliumabsorption 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 anAlpha2 Canum Venaticorum typevariable star and its brightness varies by 0.04 magnitudes over a period of 18.4 hours.[5] Its variability was discovered in 1984 by Juraj Zverko[13] and it was given its variable star designation in 1987.[14] It is around 201 million years old and is spinning with a relatively highprojected 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 itsphotosphere at aneffective temperature of 11,036 K.[7]
