James Webb measures temperature of 'Earth-like' exoplanet

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James Webb measures the temperature of an “Earth-like” exoplanet

Artistic illustration showing what exoplanet Trappist-1b, the innermost of the seven known planets in the system, might look like.

< p class="e-p">The James Webb Space Telescope has successfully measured the temperature of a rocky planet 40 light-years from our solar system, a study published in the journal Nature shows.

Discovered in 2017, the Trappist-1 system has seven planets revolving around a small, cold star, a red dwarf, half as hot as the Sun.

This planetary system is a target of choice for the James Webb Space Telescope (TSJW), developed by the American Space Agency (NASA) and in service since July 2022, one of whose missions is to probe the planet. #x27;atmosphere of potentially habitable exoplanets, beyond the solar system.

Artistic illustration showing the planets of the Trappist-1 system

Trappist-1 is an excellent laboratory for this quest, NASA points out in a press release; it is close to the solar system and has only rocky planets, all similar in size and mass to Earth.

However, it is difficult to know their characteristics, because exoplanets cannot directly observe each other at such a great distance, unlike the stars around which they orbit. To detect them, astronomers use several techniques, including transit, which captures the variations in luminosity caused by the passage of the planet in front of its host star, such as a microeclipse.

L& #x27;MIRIM imager of the TSJW, capable of observing in the mid-infrared, was able to capture a so-called secondary eclipse, when the planet passes behind its star; in this case the planet Trappist-1 b, the closest to the star Trappist-1 and therefore the easiest to study, because its transits are more numerous.

It is just before disappearing behind the star that the planet adds the most light [to that of the star], because it shows almost exclusively its day side, explains to the Agency. France-Presse Elsa Ducrot, astrophysicist at the Atomic Energy Commission (CEA) and co-author of the study published in Nature.

By comparing the amount of light detected before and during the occultation, scientists deduce the part emitted by the planet. This is light detectable only in the mid-infrared, a wavelength hitherto unexplored by astronomers, which can detect thermal emission from the planet; the TSJW acts like a giant non-contact thermometer, illustrates NASA, one of whose astrophysicists, Thomas Greene, is the lead author of the study.

Trappist-1b's temperature measurement is a first for a rocky exoplanet. It is around 230 degrees Celsius on the day side, suggesting that there is no redistribution of heat on the whole planet, a role provided by an atmosphere, specifies the CEA, which designed the MIRIM imager.

Conclusion: Trappist-1b has little or no atmosphere, says Elsa Ducrot, pointing out that we will have to dig at other wavelengths to decide. What is certain, on the other hand, is that if there is an atmosphere, it does not contain carbon dioxide, continues the astrophysicist.

That's as much details that a previous telescope, Spitzer, failed to detect despite observing 28 secondary eclipses of Trappist-1b. The James Webb saw them in a single eclipse!, welcomes the scientist.

By revealing for the first time the atmosphere around a rocky planet, the telescope developed by NASA opens a new era for the study of exoplanets, she adds.

Trappist-1 b is too close to its star to likely to harbor life forms as we know it, but observing it can provide valuable information about its sister planets, NASA confirms, including Trappist-1 e, Trappist-1 f and Trappist-1 g, which , they are in the habitable zone. This region is neither too hot nor too cold to have liquid water, a condition conducive to extraterrestrial life.

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