HD 1
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 00h 05m 08.84054s |
| Declination | +67° 50′ 23.9805″ |
| Apparent magnitude (V) | 7.42±0.01 |
| Characteristics | |
| Evolutionary stage | Red-giant branch |
| Spectral type | G9-K0 IIIa |
| Astrometry | |
| Radial velocity (Rv) | −30.177±0.007 km/s |
| Proper motion (μ) | RA: +7.480 mas/yr Dec.: −5.045 mas/yr |
| Parallax (π) | 2.668±0.0485 mas |
| Distance | 1,220 ± 20 ly (375 ± 7 pc) |
| Absolute magnitude (MV) | −0.73±0.03 |
| Orbit | |
| Period (P) | 6.3483±0.0030 yr |
| Semi-major axis (a) | ≥0.817±0.0027 AU |
| Eccentricity (e) | 0.503±0.002 |
| Periastron epoch (T) | 2,450,000 + 2,317.8±1.1 JD |
| Argument of periastron (ω) (secondary) | 221.0±0.4° |
| Semi-amplitude (K1) (primary) | 4.435±0.013 km/s |
| Details | |
| Mass | 3.5±0.1 M☉ |
| Radius | 20.7±0.3 R☉ |
| Luminosity | 217±6 L☉ |
| Surface gravity (log g) | 2.18±0.13 cgs |
| Temperature | 4,882±36 K |
| Metallicity | = −0.16±0.04 |
| Rotational velocity (v sin i) | 9.11±0.02 km/s |
| Age | 300 Myr |
| Other designations | |
| AG+67°4, BD+67°1599, HD 1, HIP 422, SAO 10963, GSC 04294-00080 | |
| Database references | |
| SIMBAD | data |
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HD 1, also known as HIP 422, is the first star catalogued in the Henry Draper Catalogue. It is located in the northern circumpolar constellation Cepheus and has an apparent magnitude of 7.42, making it readily visible in binoculars, but not to the naked eye. The object is located relatively far away at a distance of 1,220 light years but is approaching the Solar System with a spectroscopic radial velocity of −27.3 km/s.