HD 85512 b

HD 85512 b
Exoplanet List of exoplanets

Plot of the orbit of HD 85512 b compared to the star's habitable zone
Parent star
Star HD 85512
Constellation Vela
Right ascension (α) 09h 51m 07.1s
Declination (δ) −43° 30′ 10″
Apparent magnitude (mV) 7.66
Distance36 [1] ly
(11.1 ± 0.1[2] pc)
Spectral type K5 V
Mass (m) 0.69 M☉
Temperature (T) 4715 ± 102 K
Metallicity [Fe/H] −0.33 ± 0.03
Age 5.61 ± 0.61 Gyr
Orbital elements
Semi-major axis(a) 0.26 ± 0.005[2] AU
Eccentricity (e) 0.11 ± 0.1[2]
Orbital period(P) 54.43 ± 0.13[2] d
Orbital speed (υ) 94.913 ± 0.038 km/s
Physical characteristics
Minimum mass(m sin i)3.6 ± 0.5 M⊕
Stellar flux(F⊙)1.85 ⊕
Temperature (T) 298[3]
Discovery information
Discovery date August 17, 2011
Discoverer(s) Pepe et al.
Discovery method Radial velocity (HARPS)
Discovery site La Silla Observatory
Discovery status Published
Database references
Extrasolar Planets
Encyclopaedia		data
SIMBADdata
Exoplanet Archivedata
Open Exoplanet Cataloguedata
Artists’s impression of the rocky super-Earth HD 85512 b

HD 85512 b is an exoplanet orbiting Gliese 370, a K-type main-sequence star approximately 36 light-years from Earth in the constellation of Vela.[1][2]

Due to its mass of at least 3.6 times the mass of Earth, HD 85512 b is classified as a near Earth sized exoplanet (<5M⊕) and is one of the smallest exoplanets discovered to be just outside the inner edge of the habitable zone.[2] HD 85512 b, along with Gliese 581 d, was once considered to be one of the best candidates for habitability in 2011,[4] but its habitability is now disputed due to PHL's redefinition of the Habitable Zone.[5]

Detection and discovery

HD 85512 b was discovered by scientists at University of Geneva, Switzerland,[4][6] led by Swiss astronomer Stéphane Udry[7] 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.[3] 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.

Physical characteristics

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[2] and one of the most stable exoplanets discovered by the High Accuracy Radial Velocity Planet Searcher.[3]

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,[3][8] but various atmospheric conditions prevalent in the planet have to be analyzed to estimate the temperature of the surface.[3] It orbits the parent star at a distance of about 0.26 AU,[4] with an orbital period of about 54 days,[4] and possibly tidally locked.

Habitability and climate

Models generated by Pepe et al (2011) suggest that 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.[2] If the planet has 50% cloud cover, water may exist in liquid form on the planet[7] provided its atmosphere is similar to our own, thus making the planet habitable.[6][9][10] 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.[2][10]

However PHL's new definition of the Circumstellar Habitable zone puts this planet in the "too hot" zone and now considers the planet "not habitable".[11]

Possibility as target for interstellar probe

Reaching HD 85512 b at the current record spacecraft speed, the Helios Probes (247,517 km/hour | 153,800 mi/hour), it would take approximately 156,971 years.[12]

See also

Wikimedia Commons has media related to HD 85512.

References

  1. 1 2 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.
  2. 1 2 3 4 5 6 7 8 9 Kaltenegger, L; Udry, S; Pepe, F (2011). "A Habitable Planet around HD 85512?". arXiv:1108.3561. Bibcode:2011arXiv1108.3561K.
  3. 1 2 3 4 5 "HARPS: Hunting for Nearby Earth-like Planets". centauri-dreams.org. Retrieved 2011-08-25.
  4. 1 2 3 4 "Researchers find potentially habitable planet" (in French). maxisciences.com. Retrieved 2011-08-31.
  5. ↑ http://phl.upr.edu/press-releases/anewhabitablezone
  6. 1 2 "Found a planet where life could exist" (in Lithuanian). maxisciences.com. Retrieved 2011-08-31.
  7. 1 2 "Super Earth circulating in ekosferze?" (in Polish). technologie.gazeta.pl. Retrieved 2011-08-31.
  8. ↑ "Italian helps find planet that could sustain life". La Gazzetta del Mezzogiorno. September 2, 2011. Retrieved September 7, 2011.
  9. ↑ "Exoplanet Looks Potentially Lively". scientificamerican.com. Retrieved 2011-08-25.
  10. 1 2 "Is There A Habitable Planet Circling HD 85512?". spaceref.com. Retrieved 2011-08-31.
  11. ↑ http://phl.upr.edu/press-releases/anewhabitablezone
  12. ↑ "The World's Top 12 Fastest Vehicles". Popular Mechanics.

External links

Coordinates: 09h 51m 07.1s, −43° 30′ 10″

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