HR 4458
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydra |
| A | |
| Right ascension | 11h 34m 29.48644s |
| Declination | −32° 49′ 52.8228″ |
| Apparent magnitude (V) | 5.97 |
| B | |
| Right ascension | 11h 34m 30.47776s |
| Declination | −32° 50′ 02.4048″ |
| Apparent magnitude (V) | 15 |
| Characteristics | |
| Spectral type | K0 V + DC8 |
| U−B color index | 0.325 |
| B−V color index | 0.80 |
| V−R color index | 0.44 |
| R−I color index | 0.40 |
| Astrometry | |
| A | |
| Radial velocity (Rv) | −22.09±0.12 km/s |
| Proper motion (μ) | RA: –670.230 mas/yr Dec.: +822.399 mas/yr |
| Parallax (π) | 104.6133±0.0277 mas |
| Distance | 31.177 ± 0.008 ly (9.559 ± 0.003 pc) |
| Absolute magnitude (MV) | 6.05 |
| B | |
| Proper motion (μ) | RA: –701.802 mas/yr Dec.: +828.928 mas/yr |
| Parallax (π) | 104.6570 ± 0.0267 mas |
| Distance | 31.164 ± 0.008 ly (9.555 ± 0.002 pc) |
| Absolute magnitude (MV) | 15 |
| Details | |
| HR 4458 A | |
| Mass | 0.87 M☉ |
| Radius | 0.84 R☉ |
| Luminosity (bolometric) | 0.368 L☉ |
| Surface gravity (log g) | 4.59 cgs |
| Temperature | 5,241 K |
| Metallicity [Fe/H] | −0.37 dex |
| Rotational velocity (v sin i) | 6.79 km/s |
| Age | 4.6–5.8 Gyr |
| HR 4458 B | |
| Mass | 0.58 M☉ |
| Luminosity (bolometric) | 0.000088 L☉ |
| Surface gravity (log g) | 8.12 cgs |
| Temperature | 5,000 K |
| Age | 5.69 Gyr |
| Other designations | |
| 289 G. Hya, 20 Crt, CD−32°8179, GJ 432, HD 100623, HIP 56452, HR 4458, SAO 202583, LHS 308, LTT 4280, PLX 2678.00 | |
| B: WD 1132-325, VB 4 | |
| Database references | |
| SIMBAD | A |
| B | |
| ARICNS | data |
HR 4458 (HD 100623) is a binary star system 31.18 light-years away in the equatorial constellation of Hydra. It has the Flamsteed designation 20 Crateris and the Gould designation 289 G. Hydrae; the former refers to the constellation Crater, but when the IAU formally defined constellation boundaries, it was placed in Hydra. This object is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 5.97. It is moving closer to the Earth with a heliocentric radial velocity of −22 km/s.
The primary component is a K-type main-sequence star with a stellar classification of K0 V. It is around five billion years old with 84% of the Sun's radius. The star is radiating 37% of the Sun's luminosity from its photosphere at an effective temperature of 5,241 K. It has been examined for the presence of an infrared excess, but none was detected.
There is a 15th-magnitude common proper motion companion at an angular separation of 16.2″, corresponding to a projected separation of 162.5 AU. This is a white dwarf star with a classification of DC8. The orbital period of the pair is estimated as 1,110 years.