HD 85512 b
|Extrasolar planet||List of extrasolar planets|
Artist’s impression of the planet HD 85512b.
|Right ascension||(α)||09h 51m 07.1s|
|Declination||(δ)||−43° 30′ 10″|
|Distance||36  ly
(11.1 ± 0.1 pc)
|Spectral type||K5 V|
|Temperature||(T)||4715 ± 102 K|
|Metallicity||[Fe/H]||−0.33 ± 0.03|
|Age||5.61 ± 0.61 Gyr|
|Semimajor axis||(a)||0.26 ± 0.005 AU|
|Eccentricity||(e)||0.11 ± 0.1|
|Orbital period||(P)||54.43 ± 0.13 d|
|Orbital speed||(υ)||94.913 ± 0.038 km/s|
|Minimum mass||(m sin i)||3.6 ± 0.5 M⊕|
|Discovery date||August 17, 2011|
|Discoverer(s)||Pepe et al.|
|Detection method||Radial velocity (HARPS)|
|Discovery site||La Silla Observatory|
CD-42 5678 b, GJ 370 b, Gliese 370 b, HIP 48331 b, LHS 2201 b, NStars 0951-4330 b, YPC 2340 b
HD 85512 b (known as Gliese 370 b or Gl 370 b) is an extrasolar planet orbiting Gliese 370 (a K-type or “orange dwarf”) star approximately 36 light-years distance from Earth in the constellation of Vela (the Sail).
Due to its mass of at least 3.6 times the mass of Earth, HD 85512 b is classified as a super-Earth and is one of the smallest exoplanets discovered to be on the edge of the habitable zone. HD 85512 b, along withGliese 581 d is considered to be one of the best candidates for habitability as of August 30, 2011.
Detection and discovery
The planet was discovered by scientists at University of Geneva, Switzerland, led by Swiss astronomer Stéphane Udry of the Guaranteed Time Observations (GTO) program of High Accuracy Radial velocity Planet Searcher (HARPS), a high-precision echelle spectrograph installed on ESO‘s 3.6 m telescope at La Silla Observatory in Chile. The team used the Doppler spectroscopy technique which determines the minimum massof the planet through slight changes in motion of the parent star.
On August 17, 2011, researchers released a study of the planet, concluding that HD 85512 b is the most habitable exoplanet discovered up to that point and one of the most stable exoplanets discovered by the High Accuracy Radial Velocity Planet Searcher. The planet has a minimum Earth mass of 3.6 ± 0.5, surface gravity of about 1.4 g and an estimated temperature of 298 K (25 °C or 77 °F) at the top of its atmosphere. The estimated temperature is noted to be similar to temperatures in Southern France, but various atmospheric conditions prevalent in the planet have to be analyzed to estimate the temperature of the surface. It orbits the parent star at a distance of about 0.26 AU, with an orbital period of about 54 days.
Habitability and climate
For the temperature to be below 270 K (-3.15° C), for a circular orbit, the planetary albedo should be 0.48 ± 0.05 and for an eccentricity of 0.11, the planetary albedo should be 0.52. If the planet has 50% cloud cover, water may exist in liquid form on the planet provided its atmosphere is similar to our own, thus making the planet habitable. Also, if the albedo of the planet is increased due to cloud cover, water could be present in its liquid form on the planet, which would mean that the planet is on the edge of habitability.
Using the measured stellar luminosity of Gliese 370 of 0.126 times that of our Sun, it is possible to calculate HD 85512 b’s effective temperature a.k.a. black bodytemperature, which probably differs from its surface temperature. The effective temperature for HD 85512 b, assuming an aforementioned albedo, would be 24.138 °C(75 °F).
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