| Discovery | |
|---|---|
| Discovery date | 2015 November 17 |
| radial velocity method | |
| Orbital characteristics | |
| Apastron | 0.1679 (± 0.00908)AU |
| Periastron | 0.1246 (± 0.00908)AU |
| 0.1463 (± 0.0018)[1] 0.14574 (± 2e-05)[2]AU | |
| Eccentricity | 0.148 (± 0.047)[1] |
| 22.805 (± 0.005)[1]d | |
| Inclination | ?[1] |
| Star | HD 219134 |
| Physical characteristics | |
| >1.31 (± 0.02)[1]R🜨 | |
| Mass | >7.30 (± 0.40)[1]M🜨 |
Meandensity | <17.9gcm−3 |
| <4.25g | |
| Temperature | 522.6 K (249.5 °C; 481.0 °F) |
HD 219134 f, also known asHR 8832 f, is anexoplanet orbiting around theK-type starHD 219134 in the constellation ofCassiopeia. It is aSuper-Earth with aminimum mass of over 7 times that of Earth. UnlikeHD 219134 b andHD 219134 c it was not observed by theSpitzer Space Telescope and thus its radius and density are unknown. Only a minimum radius can be given.
HD 219134 f is known as a Super-Earth, a planet that's more massive than Earth but less massive thanUranus orNeptune. However, because it is not known to transit its star, only the minimum mass can be determined. The planet is at least 7.30M🜨, indicating that it could be anything from a dense rocky planet to a low-density ice giant. Gillon et al. gives the planet a minimum radius of about 1.31R🜨, which would result in an almost impossible density. For a more likely mixed composition of rock, water, and hydrogen, HD 219134 f would have a radius closer to about 2.10R🜨.
Being close to its star, HD 219134 f is hot, with an equilibrium temperature of 522.6 K (249.5 °C; 481.0 °F). Therefore, if a rocky planet, it is too hot for liquid water. It receives about 12 times the stellar flux as Earth.
HD 219134 f has an orbital period lasting about 22.72 days, only about a quarter ofMercury's, which lasts about 88 days. The planet also has an orbital radius, or semi-major axis, of 0.146AU. For comparison, Mercury orbits at 0.38 AU, and Earth at 1 AU. Because of this close proximity, HD 219134 f is likely tidally locked. The planet is near a 1:3 resonance withHD 219134 c and a 2:1 resonance withHD 219134 d.
The planet HD 219134 f orbits the K3V orange dwarf HD 219134, also known as HR 8832. It is 79% the radius and 80% the mass of the Sun with 28% the luminosity. It has a temperature of 4699 K and is around 12.5 billion years old or less. For comparison, the Sun has a temperature of 5778 K and is 4.55 billion years old.
The apparent magnitude of the star, or how bright it appears from Earth, is around 5. Therefore, it is only just visible to the unaided eye.
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