Gliese 581 c
Gliese 581 c is an extrasolar planet that orbits the red dwarf Gliese 581. He may be in the habitable zone of its solar system, ie in the area where water can exist permanently and in sufficient quantities in the liquid state due to the prevailing temperatures. The exoplanet is located in the constellation Libra, about 20.4 light-years (about 193 trillion km ) from Earth.
Properties
It takes about 13 Earth days to orbit the central star of separated only 1/14 of the Earth-Sun distance. The diameter of the planet is estimated to be one and a half times the Earth's diameter. The measurements of the discoverers of the University of Geneva provide for Gliese 581 c, a minimum mass, which corresponds to approximately five times the earth and provides a 2.2 times gravity. The specification of 1.6 g in some news is wrong. The density is higher by this factor.
With an assumed temperature of -3 to 40 ° C Gliese 581 c is the first discovered planet, could prevail on the temperature like to earth. The temperature values given are estimates, in which the reflection properties (albedo, a dark object heats up in sunlight better than a lighter) of Venus and Earth were accepted. This equilibrium temperature shall include possible set -bound rotation does not, in this case, the hemisphere temperatures would differ significantly from this value. In the case of an atmosphere of the actual surface temperature would also be increased by a natural greenhouse effect, which depends on the spectral distribution of the central star and atmosphere composition. More recent circular path and climate calculations German scientists believe that the planet is too hot to host Earth-like life forms.
The rotation of the planet is possibly bound to its orbit around its parent star: One side would therefore always facing the central star, the other always faces away. This planet would be exposed to extreme climatic conditions that divide him into a cold night and in an uninhabitable dayside. Atmospheric currents could indeed allow on the cold side of life, more likely, however, would be that this star is remote side is covered with ice.
The age of the planet is like that of the overall system Gliese 581 estimated an age of 4.3 billion years; by comparison, the Earth originated about 4.57 billion years.
Orbit
Gliese 581 c orbits its star in 13 days at a distance of 11 million km (for comparison data of the Earth's orbit: 365 days, 150 million kilometers ).
In fact, this was observed only the orbital period of 13 days; The distance was calculated from this value and the assumed mass of the star. In fact, it is among the 11 million kilometers to the semi-major axis of the orbit; in the case of a more elliptical orbit, the orbit would sometimes closer, sometimes further extend (see Kepler's laws ).
Due to the short distance, the star would appear about five times as large in the sky of the planet, such as the sun or moon in the sky of the earth.
Discovery
The planet was discovered by a team led by Stéphane Udrys Geneva Observatory with a telescope at the La Silla Observatory in Chile. The same team had already discovered Gliese 581 b. The discovery was published on 24 April 2007.
Gliese 581 c was discovered by the radial velocity method (see figure). More precise measurements are still pending. Because of the available information can be speculated about the true nature of exoplanets only because a large amount of unknown factors is present, which are reflected in the current calculations. Here are characterized both press and trade publications still a completely distorted picture.
Liquid water
Gliese is suspected in the habitable zone, where liquid water, a prerequisite for life after human understanding could exist. Nevertheless, no direct evidence for this hypothesis could be provided. But you want with the methods by which one can not detect water vapor 209458 b and HD, now also examine Gliese 581 c. But even in the case of a detection of water vapor can hardly be expected with the presence of life, as the central star Gliese 581, a variable red dwarf star is showing at irregular intervals X- ray bursts, which the fatal dose often exceed ( BY Draconis variables ).