They discover a planetary system with three super-Earths and two super-mercuries

An international scientific team has confirmed the discovery of five exoplanets in the same planetary systemtwo of them similar to Mercury. A finding that gives scientists clues about how these unusual, very high-density planets form.

The study, published this Tuesday in ‘Astronomy & Astrophysics‘, has been led by the Institute of Astrophysics of the Espaço de Portugal (IA) and the Institute of Astrophysics of the Canary Islands (IAC) participates in it, which details in a release that the planetary system found is made up of three super-earths and two super-mercuries around of the cold star HD 23472.

The leader of the study, the researcher Susana Barros, explained that they wanted to observe it to characterize the composition of small planets and to study whether or not the existence of an atmosphere could be related to the evaporation of its outer layers by the irradiation of the star.

However, “surprisingly”, they discovered that this planetary system is composed of “three super-earths with a major atmosphereand by two supermercurieswhich are the closest planets to the star”.

The five planets of the system, three of them with masses less than Earthare among the lighter exoplanets whose masses have been measured by the radial velocity method. A technique that detects small variations in the speed of the star in the line of sight due to the movement that an orbiting planet induces on it.

The discovery, as detailed by the IAC, has been possible thanks to the high precision of the spectrograph ESPRESSOinstalled at the Very Large Telescope of the European Southern Observatory in Chile.

The mysteries of Mercury

But what exactly are super earths and the supermercuries? As detailed by the IAC, they are analogues of greater mass than that of our planet and Mercury, respectively, according to their composition. They differ in that supermercuries have a higher iron contentespecially in its core: the latter are a very exceptional type of exoplanet, to the point that only eight are knownincluding the two that have just been discovered now.

mercury is one of the densest planets of our Solar System, but why is unknown it has a relatively larger and more massive core than that of the Earth and the other planets that compose it. According to the IAC, there are several theories in this regard. The most widespread holds that a body of high dimensions hit the planet and eliminated most of its original mantle, although another hypothesis attributes it to its high temperature: since Mercury is the hottest planet, part of its mantle would have evaporated .

Thus, the discovery of other dense planets similar to Mercury around other stars is key to understanding the formation of this type of planet. That is why the discovery of not one, but two supermercuries in the same planetary system is so relevant for scientists, since helps to understand how these planets were formed, as indicated by Alejandro Suárez, researcher at the IAC and co-author of the aforementioned study. “The chance of a large impact creating a supermercury is very remote, so two large impacts on the same system seems unlikely“, precise.

Objective: find another Earth

For his part, Jonay González, who is also an IAC researcher and co-author of the study, has indicated that in order to understand how these two supermercuries have been formed, it will be necessary to further characterize the composition of these planets. To this end, he pointed out, the future will be key Extremely Large Telescope (ELT) and its first-generation high-resolution spectrograph, ANDESwhich will provide the sensitivity and precision needed to probe the composition of its surface and its possible atmosphere.

For the team that has made this discovery, however, it is only the first step towards their ultimate goal: find another Earth. The researcher Barros points out that “the existence of an atmosphere would allow us to know the formation and evolution of the planetary system and also has implications for the habitability of the planets”, for which they would like to extend this type of study to “planets with a longer period than have more favorable temperatures.