[Fe/H] +0.20 Discovery status Published | Discovery date 30 July 2015 | |
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Other detection methods transiting (Spitzer telescope) Discovery site HARPS-N of the Telescopio Nazionale Galileo | ||
HD 219134 b (or HR 8832 b) is one of seven exoplanets orbiting HR 8832, a main-sequence star in the constellation of Cassiopeia. As of July 2015, super-Earth HD 219134 b, with a size of about 1.6 Earth Radii, and a density of 6g/cm3, was reported as the closest rocky exoplanet to the Earth, at 21.25 light-years away. The exoplanet was initially detected by the instrument HARPS-N of the Italian Telescopio Nazionale Galileo via the radial velocity method and subsequently observed by the Spitzer telescope as transiting in front of its star. The exoplanet has a mass of about 4.5 times that of Earth and orbits its host star every three days.
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Mass, radius and temperature
HD 219134 b is a super-Earth, an exoplanet with a radius and mass bigger than Earth, but smaller than that of the ice giants Neptune and Uranus. Its surface temperature is around 800 K (527 °C; 980 °F). It has a radius of 1.6 R⊕ and a mass of around 4.5 M⊕.
Host star
The planet orbits a (K-type) star named HR 8832, orbited by a total of seven planets. The star has a mass of 0.79 M☉ and a radius of 0.80 R☉. It has a temperature of 4710 K and is about 12.5 billion years old, making it one of the oldest stars. In comparison, the Sun is 4.6 billion years old and has a temperature of 5778 K.
The star's apparent magnitude, or how bright it appears from Earth's perspective, is 5. It can be seen with the naked eye.
Orbit
HD 219134 b orbits its host star with about 28% of the Sun's luminosity with an orbital period of 3 days and an orbital radius of about 0.03 times that of Earth's (compared to the distance of Mercury from the Sun, which is about 0.38 AU).