Thursday , April 22 2021

The TRAPPIST-1 system probably hosts the oceanic

Representative image (Archive)

At least one of the seven rocky planets orbiting the dwarf star TRAPPIST-1 could be an Earth-like oceanic world, say scientists who created up-to-date climate models for exoplanets. Researchers at the University of Washington, USA, said that because of an extremely hot and bright initial star phase, all seven star worlds may have evolved as Venus. Any primitive oceans that the planets may have evaporated, leaving behind dense and uninhabitable atmospheres.

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

TRAPPIST-1, located 39 light-years away, has about nine percent of the Sun's mass and about 12 percent of its radius. The relatively cold star "M-nan" – the most common type in the universe – has a ray only slightly larger than the planet Jupiter, although it is much larger in mass. All seven planets of TRAPPIST-1 are roughly the size of Earth and three of them – planets and, feg – are believed to be in their habitable zone, a strip of space around a star where a rocky planet could have liquid water . on its surface, giving life a chance.

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The TRAPPIST-1 d travels along the inner edge of the habitable zone, while the farther TRAPPIST-1 h orbits just past the outer edge of that zone. "This is a whole sequence of planets that can give us insight into the evolution of planets, particularly around a star that is very different from ours, with different lights coming out of it," Lincowski said.

The team's radiation and chemical models create spectral or wavelength signatures for every possible atmospheric gas, allowing observers to better predict where to look for such gases in exoplanet atmospheres. The researchers said that when traces of gases are detected by the Webb telescope, or others, someday, "astronomers will use the observed spectra to infer what gases are present – and compare it to work like ours to say something about composition of the planet, the environment and perhaps its evolutionary history. "He said that people are accustomed to thinking about the habitability of a planet around stars similar to the sun.

"But the dwarf stars M are very different, so you really have to think about the chemical effects in the atmospheres and how this chemistry affects the climate," Lincowski said. TRAPPIST-1b, the closest to the star, is a very hot burning world, even for clouds of sulfuric acid, as on Venus, to form.

The planets c and d receive a little more energy from their star than Venus and the Earth from the sun and can be similar to Venus, with a dense and uninhabitable atmosphere. The TRAPPIST-1 is the most likely of the seven to host liquid water on a temperate surface, and would be an excellent choice for additional studies with habitability in mind.
The outer planets can be similar to Venus or can be frozen, depending on the amount of water formed on the planet during its evolution. Lincowski said that, in fact, any or all of the TRAPPIST-1 planets could be similar to Venus, with any water or oceans burned for long. He explained that when water evaporates from the surface of a planet, the star's ultraviolet light separates the water molecules, releasing hydrogen, which is the lighter element and can escape the gravity of a planet.

This could leave a lot of oxygen, which could remain in the atmosphere and irreversibly remove the water from the planet. Such a planet may have a thick atmosphere of oxygen-but not one generated by life and unlike anything ever observed.

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