HD 85512 b
Encyclopedia
HD 85512 b is an extrasolar planet
orbit
ing the K-type star
Gliese 370 approximately 36 light-year
s away 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 exo-planets discovered to be in the habitable zone
. HD 85512 b, along with Gliese 581 d
is considered to be the best candidate for habitability as of August 25, 2011.
, Switzerland
, led by the Swiss astronomer Stéphane Udry
of the 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.
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.
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.
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).
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
ing the K-type star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
Gliese 370 approximately 36 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Vela
Vela (constellation)
Vela is a constellation in the southern sky. Its name is Latin for the sails of a ship, and it was originally part of a larger constellation, the ship Argo Navis, which was later divided into three parts, the others being Carina and Puppis.-Stars:...
(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
Super-Earth
A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below the mass of the Solar System's gas giants. The term super-Earth refers only to the mass of the planet, and does not imply anything about the surface conditions or habitability...
and is one of the smallest exo-planets discovered to be in the habitable zone
Habitable zone
In astronomy and astrobiology, a habitable zone is an umbrella term for regions that are considered favourable to life. The concept is inferred from the empirical study of conditions favourable for Life on Earth...
. HD 85512 b, along with Gliese 581 d
Gliese 581 d
Gliese 581 d or Gl 581 d is an extrasolar planet orbiting the star Gliese 581 approximately 20 light-years away in the constellation of Libra. It is the third planet discovered in the system and the fifth in order from the star....
is considered to be the best candidate for habitability as of August 25, 2011.
Detection and discovery
The planet was discovered by the scientists at University of GenevaUniversity of Geneva
The University of Geneva is a public research university located in Geneva, Switzerland.It was founded in 1559 by John Calvin, as a theological seminary and law school. It remained focused on theology until the 17th century, when it became a center for Enlightenment scholarship. In 1873, it...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, led by the Swiss astronomer Stéphane Udry
Stéphane Udry
Stéphane Udry is an astronomer at the University of Geneva in Switzerland, whose current work is primarily the search for extra-solar planets. He and his team, in 2007, discovered a possibly terrestrial planet in the habitable zone of the red dwarf star Gliese 581, approximately 20 light years...
of the GTO program of High Accuracy Radial velocity Planet Searcher (HARPS), a high-precision echelle spectrograph installed on ESO
ESO
ESO, as a three-letter abbreviation, may stand for:* European Southern Observatory* Ensemble Studios Online* English Symphony Orchestra* Edmonton Symphony Orchestra* Executive Stock Options...
's 3.6 m telescope at La Silla Observatory in Chile. The team used the Doppler spectroscopy
Doppler spectroscopy
Doppler spectroscopy, also known as radial velocity measurement, is a spectroscopic method for finding extrasolar planets. It involves the observation of Doppler shifts in the spectrum of the star around which the planet orbits....
technique which determines the minimum mass
Minimum mass
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets...
of the planet through slight changes in motion of the parent star.
Physical characteristics
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 exo-planets discovered by the High Accuracy Radial Velocity Planet Searcher. The planet has a minimum Earth mass of 3.6 ± 0.5, surface gravitySurface gravity
The surface gravity, g, of an astronomical or other object is the gravitational acceleration experienced at its surface. The surface gravity may be thought of as the acceleration due to gravity experienced by a hypothetical test particle which is very close to the object's surface and which, in...
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
Southern France
Southern France , colloquially known as le Midi is defined geographical area consisting of the regions of France that border the Atlantic Ocean south of the Gironde, Spain, the Mediterranean, and Italy...
, 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
Au
-Science:*Absorbance Units, a reporting unit in spectroscopy*Astronomical unit, the average distance between the Earth and the Sun *Atomic units, a system of units convenient for atomic physics and other fields...
, with an orbital period of about 54 days.
Habitability and climate
For the temperature to be below 270 K, for a circular orbit, the planetary albedoAlbedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
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.
Effective temperatures
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 temperatureEffective temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation...
a.k.a. black body
Black body
A black body is an idealized physical body that absorbs all incident electromagnetic radiation. Because of this perfect absorptivity at all wavelengths, a black body is also the best possible emitter of thermal radiation, which it radiates incandescently in a characteristic, continuous spectrum...
temperature, which probably differs from its surface temperature. The effective temperature for HD 85512 b, assuming an aforementioned albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
, would be 24.138 °C (75 °F).
See also
- Goldilocks planet
- Gliese 581 gGliese 581 gGliese 581 g , also Gl 581 g or GJ 581 g, is a hypothesized extrasolar planet proven nonexistent by the Geneva Team, orbiting the red dwarf star Gliese 581, 20.5 light-years from Earth in the constellation of Libra. It is the sixth planet discovered in the Gliese 581 planetary system and the fourth...
- Gliese 581 dGliese 581 dGliese 581 d or Gl 581 d is an extrasolar planet orbiting the star Gliese 581 approximately 20 light-years away in the constellation of Libra. It is the third planet discovered in the system and the fifth in order from the star....
- Diamond planet