In 2007, three planets were discovered in the system of the red dwarf star Gliese 581, which is about 20 light years from Earth. One of these planets is Gliese 581d, a super-Earth with only 5 times the mass of our planet. It has a 50 percent larger radius, and is located in the star's habitable zone.
After a study conducted in 2014, it was concluded that Gliese 581d was a stellar object that when corrected incompletely caused the false detection of the planet Gliese 581g. This determined that the planet Gliese 581d did not exist. New studies conducted recently ensure that the 2014 study was based on inadequate data analysis, and that Gliese 581d exists. In fact, it combines all the necessary factors to be potentially habitable.
The exoplanet Gliese 581d was discovered by the team of Stéphane Urdí, from the Geneva Observatory, in Switzerland. For this they used the HARPS instrument in the 3.6 meter telescope of the La Silla Observatory, in Chile. The team used the radial velocity technique, in which the size and mass of the planet are determined based on small variations in the orbit of its star.
The translation period of Gliese 581 around is its 66-day star. It is a planet too small to resemble a gas giant like Jupiter, but it is also too large to be a rocky planet like Earth. Its likely constitution would be water, ammonia and methane, such as Neptune or Uranus. Given the heat of the habitable zone, these substances would give rise to a sea thousands of kilometers deep.
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