The TRAPPIST-1 planets are similar in composition to the Earth

Planetologists have calculated the possible chemical compositions of the planets in the TRAPPIST-1 system and concluded that all of them, with the exception of one exomir, are very similar to our planet in terms of their subsurface and atmosphere structure, the article directed to the publication in the journal Astrophysical Journal Letters.

“The main purpose of the existence of planetology is to find planets that are similar to the Earth in terms of their chemical composition and have all the conditions for the birth of life.” We can say that astronomers have been searching for other millennia for other worlds where life can exist and be born, “says Billy Quarles) from the University of Oklahoma in Norman (USA).

In May last year, astronomers from MIT announced the discovery of an extremely unusual star system in the nearest region of the Earth – TRAPPIST-1, which is only 40 light-years away from us in the direction of the constellation of Aquarius. All three planets revolving around this red dwarf are inside the so-called “zone of life” where water can exist in liquid form, and presumably have a mass comparable to that of the earth.

Later, scientists studied the spectrum of TRAPPIST-1 star beams, trying to study the composition of the atmosphere of its planets, and they unexpectedly discovered that they were actually not three, but seven, six of them within the zone of life. All these planets have almost “terrestrial” dimensions and have a Martian or terrestrial climate, except for the first planet, TRAPPIST-1b, more like Venus than Mars or Earth.

As Quorles relates, the location of the planet within the “zone of life” is not a guarantee that life can exist on it. Even small enough exomirs, whose size or mass are only 2-3 times larger than similar parameters for the Earth, can turn out to be “ocean planets” that are unsuitable for the existence of complex life forms. In addition, they may lack an atmosphere or it may be too thick to turn them into analogs of Venus, not Earth.

For this reason, Quarles and his colleagues decided to check whether the “seven sisters” in the TRAPPIST-1 star system can be anything other than Earth analogues. To do this, scientists analyzed all known data on the passages of these planets on the red dwarf disc and tried to calculate their exact masses, density and thickness of atmospheres. In turn, based on these data, planetologists determined how much water can be present on the surface of these planets.

As these calculations showed, only one planet, TRAPPIST-1f, located in the center of the zone of life and considered one of the main candidates for the role of a twin of the Earth, is actually a “planet-ocean” – 20-25% of its mass is water. This water, thanks to a small distance to the star, will be heated to very high temperatures and will cover the planet with a dense cloud of vapor, which will make the existence of life impossible on it.

All the other six planets, they said, are more similar to the Earth – the proportion of water in their mass should not exceed several percent, and their bowels should be composed of rocks similar in composition and density to terrestrial minerals.

The most suitable for life, therefore, is not TRAPPIST-1f, but its smaller neighbor TRAPPIST-1e, located slightly closer to the luminary. In addition, life can exist on the planet TRAPPIST-1g, which makes one revolution around the star in 13 incomplete days. On their study, scientists plan to focus their efforts in the future, which, they hope, will help us to obtain more accurate data on their composition and suitability for life.

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