HD 219134
HD 219134 is a main-sequence star in the constellation of Cassiopeia. It is smaller and less luminous than the Sun, with a spectral class of K3V, which makes it an orange-hued star. HD 219134 is relatively close to our system, with an estimated distance of 21.34 light years. This star is close to the limit of apparent magnitude that can still be seen by the unaided eye. The limit is considered to be magnitude 6 for most observers.
Host star
HD 219134 is a main sequence star with a spectral classification of K3V. It has a mass and radius about three quarters that of the Sun, is somewhat cooler than the Sun at, and only 27% of its luminosity.This star has a magnitude 9.4 optical companion. The high proper motion of HD 219134 means that the separation of the companion changed from in 1852 to in 2002. The companion is a subgiant over fifty times further away than HD 219134.
Planetary system
HD 219134 has a system of at least five known exoplanets. The innermost planet, HD 219134 b, is a rocky super-Earth based on size, and density. This and three additional exoplanets; one super-Earth, one Neptunian world, and one Jovian world ; were deduced using HARPS-N radial velocity data by Motalebi et al. in 2015. Two months later, Vogt et al. published a paper on this system which found a 6-planet solution, with planets b, c & d corresponding to those in Motalebi et al., f & g being new planets, and h corresponding to Motalebi's e but with different, and more accurate, estimated parameters.A number of independent studies have been done regarding the planetary system of HD 219134, with some of their results conflicting with each other. As of March 2017, the star is known to have at least 5 planets, with two of them known to be transiting, rocky super-Earths. While a 2016 study suggested that the radial velocity signal corresponding to planet f might be caused by stellar activity, it has been confirmed by subsequent studies in 2017 and 2021. Planet g, with a 94-day period, has not been detected by subsequent studies, but some studies have found evidence of a 192-day signal which may be the true period of planet g. However, the planetary nature of this signal is unconfirmed.