An international team of astronomers has discovered a new solar system including a planet that could be "habitable", said Thursday a Spanish astrophysicist who led the research.
Three new planets have been discovered in orbit around GJ 357, a red dwarf - a small star in the cooling phase. They form a solar system located 31 light-years from Earth, a relatively short distance to the scale of space, detailed Rafael Luque of the Institute of Astrophysics of the Canary Islands.
The discovery was made thanks to the data provided by NASA's TESS satellite, specialized in the search for exoplanets - located outside our solar system.
The planet farthest from the star is of particular interest to researchers
The planet furthest from the star, named GJ 357d, is of particular interest to researchers, who believe that it could be habitable. The other two are considered too hot.
Criteria used to measure the habitability of a planet include rocky soil, a size similar to the Earth, and a distance that is neither too small nor too large in relation to its star, so that the temperature is conducive to the presence of a planet. liquid water, a key ingredient to enable the development of life.
Given its distance from its star, quite close to that between Mars and our Sun, the researchers estimate that the temperatures on the planet GJ 357d are around -53 degrees. Researchers believe that GJ 357d could be one to two times the size of the Earth.
"It seems a little cold at first sight, but if the atmosphere was dense, unlike Mars, the greenhouse effect would warm up the surface and the water could be liquid," says Rafael Luque.
A catch with the discovery method used
This planet is not the first potentially habitable to have been discovered near us. In 2016, the discovery of Proxima b, just four light-years away from our solar system, caused a stir.
The problem in these discoveries lies in the method used. Proxima b and GJ 357d were discovered by the radial velocity method, which consists in locating the oscillation caused on the star by the gravity exerted by a planet in orbit.
According to Rafael Luque, this method does not confirm whether the planet is habitable. For this, it is necessary to use the technique of transit, which makes it possible to measure its size, then to calculate its density and its composition. The planet must pass directly between its star and the observer, a difficult condition to fulfill. For Proxima b, it was impossible.
Rafael Luque and his team will try in the coming months to observe GJ 357d in "transit" to confirm if life could develop or not. "The probability that a planet passes a star in the axis of our vision from Earth is quite small