2023-06-21 09:06:20
Infrared measurements from the James-Webb Space Telescope rule out a thick carbon dioxide atmosphere for Trappist-1 c. This rocky exoplanet therefore probably does not resemble Venus as much as one might imagine.
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One after another, the planets of the Trappist-1 system are studied by the James-Webb space telescope. The atmosphere of Trappist-1b, the planet closest to the star, had already proved insignificant. It is now Trappist-1 c, the next planet in terms of distance, which has had its gaseous envelope examined. This result is the latest in the quest to determine if planetary atmospheres can survive the harsh environment of a red dwarf star.
Trappist-1 c under the gaze of the James-Webb
Trappist-1 is an Earth-sized planet (about 1.1 times the diameter of Earth and 1.3 times its mass) that circles its star, Trappist-1, in just 2.4 days. This planet is only separated from the red dwarf by 2.4 million kilometers (just over six times the Earth-Moon distance and less than one-twentieth the Sun-Mercury distance) and is 40 years- earth light.
An international team of researchers used the James Webb Space Telescope’s Miri instrument to measure the amount of heat emitted by Trappist-1c, just as another team had done to determine that Trappist-1b is likely devoid of heat. ‘atmosphere. With a daytime temperature of 107 (±31) degrees Celsius, Trappist-1c is the coldest rocky planet ever characterized using this method.
« We want to know if the rocky planets have an atmosphere or notexplains Sebastian Zieba, student at the Max-Planck Institute for Astronomy, Germany, and first author of the study published in Nature. Previously, we could only really study planets with thick, hydrogen-rich atmospheres. With Webb, we can finally start looking for atmospheres dominated by oxygen, nitrogen and carbon dioxide. »
A rocky planet with little or no atmosphere
The result suggests that the planet’s atmosphere, if it exists, is extremely thin. Indeed, although Trappist-1c is about the same size and mass as Venus and receives the same amount of radiation from its star, it seems unlikely that it has the same thick carbon dioxide atmosphere.
Although these initial measurements do not provide definitive information about the nature of Trappist-1c, they do help narrow down the likely possibilities. ” Our results are consistent with a planet that would be bare rock with no atmosphere, or a planet with a very thin CO2 atmosphere (thinner than on Earth or even Mars) with no clouds. “says Sebastian Zieba. The data also shows that the planet is unlikely to be a true analogue of Venus with a thick CO2 atmosphere and clouds of sulfuric acid.
The lack of a thick atmosphere suggests that the planet may have formed with relatively little water. If the colder planets of Trappist-1 formed under similar conditions, they too may have started out with little water and few other components needed to make a planet habitable.
In the coming year, researchers will use Webb to observe the full orbits of Trappist-1b and Trappist-1c. This will show how the temperatures change between the day and night sides of the two planets and provide additional constraints on whether or not they have atmospheres.
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