| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cetus[1] |
| Right ascension | 01h 06m 02.050s[2] |
| Declination | −22° 27′ 11.35″[2] |
| Apparent magnitude (V) | 10.16[1] |
| Characteristics | |
| Spectral type | K5V[3] |
| Apparent magnitude (B) | 11.238[1] |
| B−Vcolor index | 1.078±0.001[1] |
| Astrometry | |
| Radial velocity (Rv) | +15.28±0.23[4] km/s |
| Proper motion (μ) | RA: +203.818±0.025mas/yr[2] Dec.: −106.926±0.032mas/yr[2] |
| Parallax (π) | 19.3199±0.0198 mas[2] |
| Distance | 168.8 ± 0.2 ly (51.76 ± 0.05 pc) |
| Absolute magnitude (MV) | 7.11[1] |
| Details | |
| Mass | 0.75±0.01[5] M☉ |
| Radius | 0.69±0.02[5] R☉ |
| Luminosity | 0.19±0.01[5] L☉ |
| Surface gravity (log g) | 4.63±0.02[5] cgs |
| Temperature | 4,571±14[5] K |
| Metallicity[Fe/H] | 0.10±0.07[3] dex |
| Rotation | 42.3 days[3] |
| Age | 4.5±3.2[5] Gyr |
| Other designations | |
| CD−23°395,HIP 5158,SAO 166798,PPM 243575,LTT 617,NLTT 3632,2MASS J01060202-2227111[6] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
HIP 5158 is astar with a pair of orbitingsubstellar companions, located in theequatorialconstellation ofCetus,[1] the whale. It has the older designation CD-23 395, which is derived from theCordoba Durchmusterung catalogue of southern stars.[6] Based onparallax measurements, it is located 169 light years from the Sun. It has anabsolute magnitude of 7.11,[1] but at that distance the star has anapparent visual magnitude of 10.16,[1] which is too dim to be visible to the naked eye. The system is receding with aradial velocity of 15.3 km/s,[4] and it has a relatively highproper motion, traversing thecelestial sphere at anangular rate of0.205″·yr−1.[7]
Thespectrum of HIP 5158 matches an ordinaryK-type main-sequence star,[8] an orange dwarf, with astellar classification of K5V.[3] The age of this star is poorly constrained, but it appears to be comparable to the Sun.[5] It is spinning slowly with arotation period of around 42.3 days. Based on the abundance of iron, this star appearsmetal rich, having concentration of heavy elements equal to 125% of solar abundance.[3] It has 75% of the mass of the Sun and 60% of the Sun's radius. The star is radiating just 19% of the luminosity of the Sun from itsphotosphere at aneffective temperature of 4,571 K.[5]
In 2009, agas giant planetHIP 5158 b was found in orbit around the star. The quadratic drift in the radial velocities did indicate the presence of an additional outer planet in the system,[3] which was confirmed in 2011. The large uncertainty in the mass ofHIP 5158 c leaves in question whether this is an exoplanet or abrown dwarf.[8]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥1.42 MJ | 0.89 | 345.72 ± 5.37 | 0.52 ± 0.08 | — | — |
| c | ≥15.04 MJ | 7.7±1.88 | 9,018±3181 | 0.14±0.1 | — | — |
