HD 219134 f

HD219134 f

Discovery
Discovery date	2015 November 17
Detection method	radial velocity method
Orbital characteristics
Apastron	0.1679 (± 0.00908)AU
Periastron	0.1246 (± 0.00908)AU
Semi-major axis	0.1463 (± 0.0018) 0.14574 (± 2e-05)AU
Eccentricity	0.148 (± 0.047)
Orbital period (sidereal)	22.805 (± 0.005)d
Inclination	?
Star	HD 219134
Physical characteristics
Mean radius	>1.31 (± 0.02)R🜨
Mass	>7.30 (± 0.40)ME
Meandensity	<17.9gcm−3
Surface gravity	<4.25g
Temperature	522.6 K (249.5 °C; 481.0 °F)

HD 219134 f,also known asHR 8832 f,is anexoplanetorbiting around theK-type starHD 219134in the constellation ofCassiopeia.It is aSuper-Earthwith aminimum massof over 7 times that of Earth. UnlikeHD 219134 bandHD 219134 cit was not observed by theSpitzer Space Telescopeand thus its radius and density are unknown. Only a minimum radius can be given.

Characteristics

Mass, Radius, and Temperature

HD 219134 f is known as a Super-Earth, a planet that's more massive than Earth but less massive thanUranusorNeptune.However, because it is not known to transit its star, only the minimum mass can be determined. The planet is at least 7.30M_E,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.

Orbit

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 cand a 2:1 resonance withHD 219134 d.

Host Star

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.