The James Webb Space Telescope has succeeded in measuring the temperature of a rocky planet 40 light-years from our solar system, in a first-ever operation, a study reported Monday.

Discovered in 2017, the TRAPPIST-1 system includes seven planets orbiting a supercool red dwarf star that emits twice as much heat as the sun.

This planetary system is a major target of the James Webb Telescope, which was developed by the US Space Agency (NASA) and put into service in July 2022.

One of the telescope's tasks is to explore the atmospheres of potentially habitable exoplanets.

NASA said in a statement that "+ TRAPPIST-1 + is an excellent planet for testing," as it is close to the solar system and includes only rocky planets similar in size and mass to Earth.

However, knowing the characteristics of these planets is a difficult issue because it is not possible to observe the outer planets from a great distance, in contrast to the stars that revolve around them.

To observe it, astronomers resort to a method that consists in capturing differences in the brightness of the planet caused by it passing in front of its host star, similar to what happens in a small eclipse.

James Webb's "Merim" imaging device, which is capable of operating in the mid-infrared wavelength, was able to capture the so-called secondary eclipse when the planet passes behind its star, and in this case, the planet is "TRAPPIST-1b" closest to the star "TRAPPIST-1". Which is easy to study because it crosses a lot behind the star.

Elsa Ducros, an astrophysicist at the Commission for Atomic Energy and Alternative Energies and co-author of the study published in the journal "Nature", explains that "the largest brightness of the planet occurs moments before it disappears behind the star because it shows its day side almost exclusively."

By comparing the amount of light observed before and after the planet disappeared behind its star, the scientists deduced the amount of light emitted by the planet, which can only be detected in the mid-infrared wavelength, a wavelength astronomers have yet to explore that would detect the planet's heat emission.

NASA, whose astronomer, Thomas Green, prepared the study, commented that James Webb acts as a "giant non-contact thermometer."

Measuring the temperature of TRAPPIST 1b is the first such procedure for a rocky exoplanet.

The temperature on the daytime side of the planet was about 230 degrees Celsius, an indication that heat was not redistributed throughout the planet, a role usually played by the atmosphere,” according to the Commission for Atomic Energy and Alternative Energies, which designed the “Miriam” device.

And Ducron says that the conclusion is, therefore, that the planet "Trapiste 1b" "has little or no atmosphere," stressing the need to search in other wavelengths to reach a final result.

"What is certain is that the atmosphere, even if it is present in the planet, lacks carbon dioxide," she added.

James Webb's discovery bears the details of the failure of a previous telescope, "Spitzer", to reach it, "despite the observation of 28 secondary eclipses of +TRAPPIST -1b +".

And the scientist says, "James Webb deduced these details by observing one eclipse!"

She noted that James Webb, by studying the possibility of an atmosphere in a rocky planet, launches a "new phase" in the study of exoplanets.

Trappist 1b is located so close to its star that it could house life as we know it, and its monitoring may provide important information about other planets, according to NASA.

Among these planets are "TRAPPIST-1E", "TRAPPIST-1F" and "TRAPPIST-1G", which are located in a habitable zone, which is an area that is not very hot or cold, which allows the formation of liquid water in it, which is a prerequisite for life outside life. Planet Earth.