| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 00h58m 14.21894s[1] |
| Declination | +33° 57′ 03.1841″[1] |
| Apparent magnitude (V) | +5.98[2] |
| Characteristics | |
| Evolutionary stage | Red giant branch[3] |
| Spectral type | K0 IV[4] |
| B−V color index | 1.016[2] |
| Astrometry | |
| Radial velocity (Rv) | −23.13±0.12[1] km/s |
| Proper motion (μ) | RA: 36.459 mas/yr[1] Dec.: -71.320 mas/yr[1] |
| Parallax (π) | 17.0697 ± 0.0302 mas[1] |
| Distance | 191.1 ± 0.3 ly (58.6 ± 0.1 pc) |
| Absolute magnitude (MV) | +2.11[4] |
| Orbit[5] | |
| Period (P) | 146+74 −37 yr |
| Semi-major axis (a) | 0.524+0.151 −0.084" (30.7+8.8 −4.9 AU) |
| Eccentricity (e) | 0.53+0.18 −0.26 |
| Inclination (i) | 147.5+6.6 −13° |
| Longitude of the node (Ω) | 141+56 −48° |
| Periastron epoch (T) | 2,472,895+17,464 −5,098 |
| Argument of periastron (ω) (secondary) | 257+32 −35° |
| Details[6] | |
| HD 5608 A | |
| Mass | 1.50±0.04 M☉ |
| Radius | 5.0±0.1 R☉ |
| Luminosity | 13.1±0.3 L☉ |
| Surface gravity (log g) | 3.20±0.02 cgs |
| Temperature | 4,897±25 K |
| Metallicity [Fe/H] | +0.12±0.03[3] dex |
| Rotational velocity (v sin i) | 1.37[4] km/s |
| Age | 3.0±0.3 Gyr |
| HD 5608 B | |
| Mass | 0.10±0.01[7] M☉ |
| Mass | 121.2+8.3 −7.0[5] MJup |
| Other designations | |
BD+33° 140, FK5 2061, HD 5608, HIP 4552, HR 275, SAO 54306[8] | |
| Database references | |
| SIMBAD | data |
HD 5608 is an orange-hued star in the northern constellationofAndromeda with one known planet, HD 5608 b.[4] It is a dim star near the lower limit of visibility to the naked eye, having an apparent visual magnitude of +5.98.[2] The distance to HD 5608, as estimated from an annual parallax shiftof17.07 mas,[1] is 191 light-years (59parsecs). It is moving closer to the Earth with a heliocentric radial velocity of −23 km/s,[1] and is expected to make its closest approach in 1.285 million years when it comes to within 124 light-years.[9]
This is a K-type subgiant star on the red giant branch track with a stellar classification of K0 IV.[4] It has 1.5 times the mass of the Sun and, at the age of three billion years, has expanded to five times the Sun's radius. It is radiating 13 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,897 K. It has a higher than solar metallicity – a term astronomers use to describe the abundance of elements other than hydrogen and helium.[6]
HD 5608 has a co-moving companion, HD 5608 B, at an angular separationof0.6″, which has been directly imaged. The physical separation of the pair is calculated as 40±1 AUor47±3 AU, depending on the assumptions. It has an H band magnitude difference of 9.40 with the primary and an estimated mass of 0.10 M☉. A second companion at a separation of 7.4″ is a background star.[7] This companion star has since been characterized by radial velocity and astrometry in addition to imaging.[5]
In 2012, the Okayama Planet Search Program reported the detection of a substellar companion in orbit around HD 5608, based upon Doppler measurements between 2003 and 2011 from the Okayama observatory in Kurashiki. These showed a linear trend indicating the existence of a distant companion. The data showed an additional periodicity of around 766 days. This object shows a minimum mass of 1.4 MJ, a semimajor axisof1.9 AU, and an eccentricity of 0.19.[4] The high eccentricity of this planet could have been induced by the low mass companion star HD 5608 B via the Kozai mechanism.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥1.168+0.062 −0.057 MJ |
1.790+0.007 −0.003 |
768.70+4.72 −1.67 |
0.110+0.029 −0.080 |
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