A team of researchers calculates the characteristics that a planet similar to ours should have in the closest star system to us
With almost 5,000 exoplanets discovered, and a number that continues to rise every day, the search for a ‘new Earth’ is entering a whole new phase. In fact, simply cataloging thousands of new worlds is no longer enough. Now it is a question of characterizing the most promising ones, analyzing their atmospheres, and looking for signs of life in them. Something technically impossible until now, but that new telescopes, such as the James Webb, launched on Christmas Day last year, or the ELT (Extremely Large Telescope), currently under construction, will be able to tackle in the coming years.
But what exactly should they be looking for? Or put another way, what would an ‘Earth’ orbiting a Sun-like star look like? To find out, a team of researchers from the ETH Zurich, known simply as ETH Zurich, has set out to find out what the elemental composition of a hypothetical planet would be in the habitable zone of the two closest Sun-like stars to us: Alpha Centauri A and Alpha Centauri B.
Or put another way, what would an Earth-like planet look like in that star system? The results of this work have just been published in ‘The Astrophysical Journal.
At about 4.36 light-years away, Alpha Centauri is the closest star system to Earth. It is made up of three stars, Alpha Centauri A (or Rigil Kentaurus), Alpha Centauri B (or Tolimán) and Alpha Centauri C (or Próxima Centauri, as it is the closest to the Sun). The model carried out by the researchers is based on the chemical compositions measured by spectroscopy in the first two (the third is a red dwarf, very different from the Sun), of which, due to their proximity, a large quantity is available. of information.
From these data, the ETH Zurich scientists were able to project the possible compositions that a hypothetical planetary body orbiting either of the two stars would have. And so they arrived at extremely detailed predictions about the properties of their model planet, which they named ‘ α-Cen-Earth ‘ (Earth of Alpha Centauri), including its internal structure, mineralogy, and atmospheric composition.
This would be the ‘new Earth’
Under the direction of astrophysicist Haiyang Wang, the team of researchers has managed to draw a captivating image of a possible exoplanet in Alpha Centauri A or B. According to the article, if it really exists, it is very likely that α-Cen-Earth has very interesting geochemistry. similar to that of our Earth, with a silicate-dominated mantle, but enriched with carbon-containing elements such as graphite and diamond. The water storage capacity in its rocky interior should also be equivalent to that of our home planet.
But not everything would be similar. According to the study, α-Cen-Earth would also differ from Earth in several ways, with a slightly larger iron core, less geological activity, and a possible lack of plate tectonics. The biggest surprise, however, was that the hypothetical planet’s early atmosphere could have been dominated by carbon dioxide, methane, and water, just as Earth’s was in the Archean Eon, between 4 and 2.5 billion years ago, when the planet emerged. first life on our planet.
Predictions about the atmosphere
The study also stands out because the model is capable of including predictions about the presence of volatile elements. Something extremely complicated since, although it is known that the chemical composition of rocky or ‘terrestrial’ planets normally corresponds to that of their host stars, that is valid only for the so-called ‘ refractory elements ‘, that is, rocks and metals. But the correspondence breaks down for volatile elements, which are those that evaporate easily, such as hydrogen, carbon, and nitrogen, which are key to understanding whether a planet is potentially habitable.
The probability of finding a ‘big brother’ to our Earth (the Alpha Centauri A/B system is between 1.5 and 2 billion years older than the Sun) could hardly be more favorable. And between 2022 and 2035, Alpha Centauri A and Alpha Centauri B will be far enough apart to begin searching for worlds around each of the two stars without the hindrance of the nearby star’s brightness. In fact, and taking advantage of the powerful new generation of telescopes, researchers are hopeful that one or more exoplanets around Alpha Centauri A/B will join the nearly 5,000 exoplanets that have been discovered since 1995 when astrophysicists at the University of Geneva Michel Mayor and Didier Queloz(who joined the ETH Zurich faculty last year) announced the discovery of the first planet outside our Solar System around a Sun-like star.
The work of Wang and his colleagues, therefore, is important so that the next efforts to search for planets in the Alpha Centauri system have a solid base on which to rest and a series of well-defined characteristics of the worlds that are intended to be located.
