HD 5608 is an orange-huedstar in the northernconstellation ofAndromeda with one known planet, HD 5608 b.[5] It is a dim star near the lower limit of visibility to the naked eye, having anapparent visual magnitude of +5.98.[3] The distance to HD 5608, as estimated from an annualparallax shift of17.07 mas,[2] is 191light-years (59parsecs). It is moving closer to the Earth with a heliocentricradial velocity of −23 km/s,[2] and is expected to make its closest approach in 1.285 million years when it comes to within 124 light-years.[11]
HD 5608 has a co-moving companion, HD 5608 B, at anangular separation of0.6″, which has been directly imaged. The physical separation of the pair is calculated as40±1 AU or47±3 AU, depending on the assumptions. It has anH band magnitude difference of 9.40 with the primary and an estimated mass of 0.10 M☉. A second companion at a separation of7.4″ is a background star.[9] This companion star has since been characterized byradial velocity andastrometry in addition to imaging.[6]
In 2012, theOkayama Planet Search Program reported the detection of a substellar companion in orbit around HD 5608, based uponDoppler measurements between 2003 and 2011 from the Okayama observatory inKurashiki. 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 of1.4MJ, asemimajor axis of1.9 AU, and aneccentricity of 0.19.[5] The high eccentricity of this planet could have been induced by the low mass companion star HD 5608 B via theKozai mechanism.[9]
^abcHøg, E.; et al. (200). "The Tycho-2 catalogue of the 2.5 million brightest stars".Astronomy & Astrophysics.355:L27–L30.Bibcode:2000A&A...355L..27H.
