HD 21278
Binary star system in the constellation Perseus
From Wikipedia, the free encyclopedia
HD 21278 is a binary star[10] system in the constellation Perseus, located within the Alpha Persei Cluster.[10] 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 570 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]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Perseus |
| Right ascension | 03h 28m 03.07076s[1] |
| Declination | 49° 03′ 46.3258″[1] |
| Apparent magnitude (V) | 4.99[2] |
| Characteristics | |
| Evolutionary stage | Main sequence[3] |
| Spectral type | B5V + B9V[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: +22.754 mas/yr[1] Dec.: −25.649 mas/yr[1] |
| Parallax (π) | 5.6775±0.1248 mas[1] |
| Distance | 570 ± 10 ly (176 ± 4 pc) |
| Absolute magnitude (MV) | −1.49[6] |
| Orbit[3] | |
| Period (P) | 21.685415±0.000035 days |
| Semi-major axis (a) | 1.75820±0.00377 mas |
| Eccentricity (e) | 0.13843±0.00010 |
| Inclination (i) | 148.938±0.030° |
| Longitude of the node (Ω) | 85.725±0.049° |
| Periastron epoch (T) | mJD 46714.031±0.022 |
| Argument of periastron (ω) (secondary) | 89.946±0.049° |
| Semi-amplitude (K1) (primary) | 31.45±0.31 km/s |
| Semi-amplitude (K2) (secondary) | 50.47±0.31 km/s |
| Details[3] | |
| A | |
| Mass | 5.381±0.084 M☉ |
| Radius | 3.75±0.09 R☉ |
| Luminosity | 940[6] L☉ |
| Surface gravity (log g) | 4.152±0.113[7] cgs |
| Temperature | 16,750 K |
| Metallicity [Fe/H] | 0.00[8] dex |
| Rotational velocity (v sin i) | 53 km/s |
| Age | 49.5±6.0 Myr |
| B | |
| Mass | 3.353±0.064 M☉ |
| Temperature | 11,120 K |
| Age | 49.5±6.0 Myr |
| Other designations | |
| BD+48°920, GC 4108, HD 21278, HIP 16147, HR 1034, SAO 38849[9] | |
| Database references | |
| SIMBAD | data |
The binary nature of this star was announced in 1925 by Otto Struve.[11] It is a double-lined spectroscopic binary with an orbital period of 21.685 days and an eccentricity of 0.138.[3]
The primary component is a B-type main-sequence star with a stellar classification of B5V, indicating it is generating energy through core hydrogen fusion. The star is spinning with a projected rotational velocity of 53 km/s. It has 5.381 times the mass of the Sun and about 3.75 times the Sun's radius.[3] HD 21278 A is radiating 940 times the luminosity of the Sun[6] from its photosphere at an effective temperature of 16,410 K.[3]
The secondary component is also a B-type main-sequence star, with a spectral class B9V. It has 3.353 times the mass of the Sun and an effective temperature of 11,120 K.[3]