| |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Perseus |
| Right ascension | 03h28m 03.07229s[1] |
| Declination | 49° 03′ 46.3315″[1] |
| Apparent magnitude (V) | 4.99[2] |
| Characteristics | |
| Spectral type | B5V[3] |
| U−B color index | −0.56[4] |
| B−V color index | −0.10[4] |
| Astrometry | |
| Radial velocity (Rv) | +1.20[5] km/s |
| Proper motion (μ) | RA: +21.784[1] mas/yr Dec.: −26.036[1] mas/yr |
| Parallax (π) | 5.6334 ± 0.2298 mas[1] |
| Distance | 580 ± 20 ly (178 ± 7 pc) |
| Absolute magnitude (MV) | −1.49[6] |
| Orbit[7] | |
| Period (P) | 21.695±0.004 d |
| Semi-major axis (a) | ≥6.72 Gm |
| Eccentricity (e) | 0.12±0.04 |
| Periastron epoch (T) | 24,446,714.5±0.2 |
| Argument of periastron (ω) (secondary) | 109±3° |
| Semi-amplitude (K1) (primary) | 22.7±0.9 km/s |
| Semi-amplitude (K2) (secondary) | 49±3 km/s |
| Details | |
| A | |
| Mass | 4.597[8] M☉ |
| Radius | 3.9[9] R☉ |
| Luminosity | 940[6] L☉ |
| Surface gravity (log g) | 4.152±0.113[10] cgs |
| Temperature | 15,274±244[10] K |
| Metallicity [Fe/H] | 0.00[11] dex |
| Rotational velocity (v sin i) | 75[10] km/s |
| Age | 187[11] or 60[6] Myr |
| Other designations | |
BD+48°920, GC 4108, HD 21278, HIP 16147, HR 1034, SAO 38849[12] | |
| Database references | |
| SIMBAD | data |
HD 21278 is a binary star[7] system in the constellation Perseus, located within the 60±7[6] million year old Alpha Persei Cluster.[7] It has a blue-white hue and is visible to the naked eye with a combined apparent visual magnitude of 4.99.[2] The system is located at a distance of approximately 580 light years from the Sun based on parallax,[1] and it is drifting further away with a radial velocity of +1.20 km/s.[5]
The binary nature of this star was announced in 1925 by Otto Struve.[13] It is a double-lined spectroscopic binary with an orbital period of 21.7 days and an eccentricity of 0.12.[7]
The primary component is a B-type main-sequence star with a stellar classification of B5V,[3] indicating it is generating energy through core hydrogen fusion. The star is spinning with a projected rotational velocity of 75 km/s.[10] It has 4.6[8] times the mass of the Sun and about 3.9[9] times the Sun's radius. HD 21278 is radiating 940[6] times the luminosity of the Sun from its photosphere at an effective temperature of 15,274 K.[10]
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