HD 85512 b
|Extrasolar planet||List of extrasolar planets|
|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.|
|Discovery method||Radial velocity (HARPS)|
|Discovery site||La Silla Observatory|
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 with Gliese 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 mass of the planet through slight changes in motion of the parent star. It was discovered on August 17, 2011.
On August 17, 2011, researchers released a study of the planet. The study makes assumptions about the planet actually having the minimum mass allowed by existing observations, not being tidally locked, and having one specific composition out of the wide parameter set available to conclude 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, minimum surface gravity of about 1.4 g and assuming an atmosphere like Earth's despite its far greater mass, an estimated temperature of 298 K (24.85 °C or 76.73 °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, and possibly tidally locked.
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.
Based on the bolometric luminosity of its parent star, the planet would receive 1.86 times as much light as Earth does from the Sun. This amount is only slightly less than Venus at 1.92, suggesting that it may have suffered a runaway greenhouse effect.. However, if the planet has been tidally locked shortly after formation, stabilizing cloud feedback may prevent the runaway greenhouse effect. 
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 body temperature, 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).
Possibility as target for interstellar probe
- Diamond planet
- Earth analog
- Gliese 581 d
- Gliese 581 g
- Gliese 667 Cc
- Goldilocks planet
- Habitable zone
- Kepler 22 b
- Planetary habitability
|Wikimedia Commons has media related to HD 85512.|
- Pepe, F; et al. (2011). The HARPS search for Earth-like planets in the habitable zone: I – Very low-mass planets around HD20794, HD85512 and HD192310. arXiv:1108.3447. Bibcode:2011yCat..35349058P. doi:10.1051/0004-6361/201117055.
- Kaltenegger, L; Udry, S; Pepe, F (2011). A Habitable Planet around HD 85512?. arXiv:1108.3561. Bibcode:2011arXiv1108.3561K.
- "HARPS: Hunting for Nearby Earth-like Planets". centauri-dreams.org. Retrieved 2011-08-25.
- "Researchers find potentially habitable planet" (in French). maxisciences.com. Retrieved 2011-08-31.
- "Found a planet where life could exist" (in Lithuanian). maxisciences.com. Retrieved 2011-08-31.
- "Super Earth circulating in ekosferze?" (in Polish). technologie.gazeta.pl. Retrieved 2011-08-31.
- "Italian helps find planet that could sustain life". La Gazzetta del Mezzogiorno. September 2, 2011. Retrieved September 7, 2011.
- "Exoplanet Looks Potentially Lively". scientificamerican.com. Retrieved 2011-08-25.
- "Is There A Habitable Planet Circling HD 85512?". spaceref.com. Retrieved 2011-08-31.
- Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets
- Potentially habitable "Super-Earth" is among 50 newly discovered exoplanets
- "The World's Top 12 Fastest Vehicles". Popular Mechanics.