HIP 5158
Star in the constellation Cetus
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HIP 5158 is a star with a pair of orbiting substellar companions, located in the equatorial constellation of Cetus,[1] the whale. It has the older designation CD-23 395, which is derived from the Cordoba Durchmusterung catalogue of southern stars.[6] Based on parallax measurements, it is located 169 light years from the Sun. It has an absolute magnitude of 7.11,[1] but at that distance the star has an apparent visual magnitude of 10.16,[1] which is too dim to be visible to the naked eye. The system is receding with a radial velocity of 15.3 km/s,[4] and it has a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.205″·yr−1.[7]
| 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−V color index | 1.078±0.001[1] |
| Astrometry | |
| Radial velocity (Rv) | +15.28±0.23[4] km/s |
| Proper motion (μ) | RA: +203.818±0.025 mas/yr[2] Dec.: −106.926±0.032 mas/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 |
The spectrum of HIP 5158 matches an ordinary K-type main-sequence star,[8] an orange dwarf, with a stellar 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 a rotation period of around 42.3 days. Based on the abundance of iron, this star appears metal 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 its photosphere at an effective temperature of 4,571 K.[5]
Planetary system
In 2009, a gas giant planet HIP 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 of HIP 5158 c leaves in question whether this is an exoplanet or a brown 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 | — | — |