An exoplanet half as massive as Earth, but denser and much warmer, has been discovered around a nearby red dwarf. This object, of an unusual type among those discovered to date, will help to better understand the origin of these planets.
are known to date, discovered in more than 3,500 planetary systems. However, of these, less than 200 have lower than those of Earth. Those , althougha priori many, remain in fact .
In a new study published in, an international group of 78 researchers, led by Kristine WF Lam and Szilárd Csizmadia of the ( ), adds a new member to this : GJ 367b.
A nearby underground …
This planet, located just under 31of the Earth, was discovered thanks to the detection of its speak Transiting Exoplanet Survey Satellite ( ). The satellite measurements of the allowed to determine its diameter: 72% of (12,742 km), or just over 9,000 kilometers. ” This places it among the terrestrial planets of and advance the search for a “second Earth” », Explains Kristine Lam. To compare, has an average diameter of 12,104 kilometers and Mars of 6,779 kilometers.
Son, the GJ 367, about half the size of the , was then studied from the ground using the radial velocity method. The of the planet was determined using the Harps, installed on the of 3.6 meters from the European Southern Observatory, and evaluated at 55% of the mass of the Earth. Venus and Mars, for their part, have masses equal to 81.5% and 10.7% of that of the Earth. This result makes GJ 367 b one of the lightest planets known to date and places it in the category of sub-Earth, that is to say planets significantly less massive than Earth and Venus.
… or rather an overheated super-Mercury
By determining its radius and mass with an accuracy of 7 and 14% respectively, the researchers were able to deduce that this planet is. Its average density, equal to almost one and a half times that of the Earth, ” indicates that the planet is dominated by a nucleus of . These properties are similar to those of Mercury, with disproportionate which differentiates it from other telluric bodies of the solar system », Précise Szilárd Csizmadia.
However, the planet’s proximity to its star means it is exposed to an extremely high level of radiation, more than 500 times stronger than what Earth is experiencing. Indeed, this planet takes only about eight hours to circle its mother star. The temperature on its surface could thus reach up to 1,500, what to do . GJ 367 b therefore clearly cannot be regarded as a ” ».
GJ 367 b belongs to the group of exoplanets with, which orbit their star in less than 24 hours. ” We already know a few, but their origins are currently unknown., says Kristine Lam. By measuring the precise fundamental properties of [cette] planet, we can gain insight into the history of the formation and evolution of the system ».
What you must remember
- GJ 367 b, an exoplanet half the size of Earth, but denser and much warmer, has been discovered around a red dwarf 31 light years away from us.
- The proximity of this planetary system makes it ideal for further investigation.
- The discovery demonstrates that it is possible to accurately determine the properties of the smallest and least massive exoplanets.
- Such studies provide a key to understanding how the terrestrial planets form and evolve.