The TRAPPIST-1 system probably hosts an oceanic world similar to Earth

At least one of the seven rocky planets orbiting the dwarf star TRAPPIST-1 could be an ocean-like world, say scientists who have created updated climate models for exoplanets. Researchers at the University of Washington in the United States said that because of a very hot and bright early star phase, the seven worlds of the star might have evolved as Venus. All the primitive oceans that the planets could have evaporated have left a dense and uninhabitable atmosphere.

"We are modeling unknown atmospheres, not just assuming that the things we see in the solar system are similar to one another," said Andrew Lincowski, a Ph.D. student at the University of Washington. "We conducted this research to show what these different types of atmosphere might look like," said Lincowski, lead author of the study published in Astrophysical Journal.

TRAPPIST-1, located 39 light-years away, has about 9% of the Sun's mass and about 12% of its radius. The relatively "M dwarf" star, the most prevalent type in the universe, has a radius of a little larger than the planet Jupiter, although its mass is much larger.

The seven planets of TRAPPIST-1 are about the size of the Earth and three of them – the planets labeled e, f, and g – would be in its habitable zone, this band of space around A star where a rocky planet could have liquid water on its surface, thus giving a chance to life. TRAPPIST-1 d travels the inner edge of the habitable zone, while TRAPPIST-1 h, farther away, revolves around the outer edge of this zone.

"It's a whole sequence of planets that can give us a glimpse of their evolution, especially around a star very different from ours, whose light differs," said Lincowski. The team's radiation and chemistry models create spectral or wavelength signatures for each possible atmospheric gas, allowing observers to better predict where to look for these gases in exoplanet atmospheres.

The researchers said that when the Webb telescope or other people detect traces of gas, astronomers will use the bumps and ripples observed in the spectrum to infer which gases are present – and will compare it to function as the our. the composition of the planet, its environment and perhaps its evolutionary history. He said people are used to thinking about the livability of a planet around sun-like stars.

"But dwarf M stars are very different, so you really have to think about the chemical effects on atmospheres and how that chemistry affects the climate," Lincowski said. TRAPPIST-1B, the closest to the star, is a blazing world too hot, even for clouds of sulfuric acid, as on Venus, to form. The planets c and d receive slightly more energy from their star than Venus and the Earth from the sun and could look like Venus, with a dense and uninhabitable atmosphere.

TRAPPIST-1 is the most likely of the seven to harbor liquid water on a temperate surface and would be an excellent choice for further studies taking into account habitability. The outer planets f, g and h could look like Venus or be frozen, depending on the amount of water formed on the planet during its evolution.

Lincowski said that in fact, all or part of the TRAPPIST-1 planets might look like Venus's, with water or oceans burned for a long time. He explained that when water evaporates from the surface of a planet, the ultraviolet light of the star breaks water molecules, releasing hydrogen, which is the lightest element and can escape to the gravity of the planet.

This could leave a lot of oxygen, which could remain in the atmosphere and irreversibly eradicate water from the planet. Such a planet can have a thick oxygen atmosphere – but not generated by life and different from all that has already been observed.