Free Astronomy Magazine March-April 2022

51 MARCH-APRIL 2022 ASTRO PUBLISHING With the meticulous study and com- bination of different evaluation methods, the radius and mass of the planet were accurately determined: its radius is 72 percent of Earth’s ra- dius, and its mass 55 percent of Earth’s mass. By determining its ra- dius and mass with an accuracy of 7 and 14 percent respectively, the re- searchers were also able to draw conclusions about the exoplanet’s inner structure. It is a low-mass rocky planet, but has a higher density than the Earth. “ The high density indi- cates the planet is dominated by an iron core,” explains Szilárd Csizma- dia co-author of the article from the DLR. “These properties are similar to those of Mercury, with its dispropor- tionately large iron and nickel core that differentiates it from other ter- restrial bodies in the Solar System.” However, the planet’s proximity to its star means it is exposed to an ex- treme high level of radiation, more than 500 times stronger than what the Earth experiences. “The surface temperature could reach up to 1500 degrees Celsius – a temperature at which all rocks and metals would be melted. GJ 367 b therefore cannot be considered a ‘second Earth’” notes Enric Pallé, a researcher at the IAC who has also participated in the study. The parent star of this newly discov- ered exoplanet, a red dwarf called GJ 367, is only about half the size of the Sun. This was beneficial for its discovery as the transit signal of the orbiting planet is particularly sig- nificant. “Red dwarfs are not only smaller, but also cooler than the Sun. This makes their associated planets easier to find and characterise” , says Felipe Murgas co-author of the arti- cle from the IAC. Red dwarfsare among the most common stellar objects in our cosmic neighbourhood and are therefore suitable targets for exoplanet re- search. Researchers estimate that these red dwarfs, also known as ‘class M stars’, are orbited by an av- erage of two to three planets, each of which is at most four times the size of Earth. ! A n artist’s simu- lation of the subterrestrial planet GJ 367 b. [DLR]