Tuesday, January 5, 2016

HD 85512b is a Potentially Habitable Super-Earth

HD 85512b is a potentially habitable super-Earth with at least 3.6 times the mass of Earth. Its host star is a K5V star that is less massive and much less luminous than the Sun. A planet around such a star has to orbit much closer in than Earth is from the Sun in order to receive a similar level of insolation as what Earth gets from the Sun. HD 85512b orbits its host star at 0.26 AU and its orbital period is 58.4 days.

Figure 1: Artist’s impression of a potentially habitable planet.

The distance of HD 85512b from its host star places it within the habitable zone. The habitable zone is a range of distances from a star where it is neither too hot nor too cold for a planet to sustain liquid water on its surface, and possibly even life. The estimated equilibrium temperature on HD 85512b is 298 K, or 25°C. Although HD 85512b is within the habitable zone of its host star, it is closer to the warm inner edge of the habitable zone.

HD 85512b was detected through radial velocity measurements by the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph. The planet gravitationally tugs its host star, causing its host star to wobble by as much as 0.769 ± 0.090 m/s. The strength and periodicity of this wobbling allows the mass and orbital period of the planet to be determined.

Figure 2: Phase-folded radial velocity curve indicating the presence of the potentially habitable super-Earth HD 85512b. F. Pepe et al. (2011)

F. Pepe et al. (2011), “The HARPS search for Earth-like planets in the habitable zone: I -- Very low-mass planets around HD 20794, HD 85512 and HD 192310”, arXiv:1108.3447 [astro-ph.EP]