According to a study published on Monday, the James Webb Space Telescope managed to measure for the first time the temperature of a rocky planet, which is considered to be a “cousin” of Earth, located 40 light years from our solar system, AFP and Yahoo News reported. , reports Agerpres.

Discovered in 2017, the Trappist-1 system consists of seven planets orbiting a small “cold” star, a red dwarf, half as hot as the Sun.

This planetary system is the target of the James Webb Telescope (JWST), developed by the American space agency NASA and operating from July 2022.

One of its missions is to study the atmospheres of potentially habitable exoplanets located outside the solar system.

Trappist-1 is an “excellent laboratory” for the search, NASA said in a statement: It is close to the solar system and contains only rocky planets, all similar to Earth in size and mass.

How astronomers study distant exoplanets

However, knowing the characteristics of these planets outside our solar system is difficult because exoplanets cannot be directly observed at such a great distance, unlike the stars they orbit.

To detect them, astronomers use the transit method, which captures fluctuations in brightness caused by the passage of a planet through the host star, as a micro-eclipse.

The telescope’s Mid-Infrared Imager Module (MIRIM) instrument, capable of observing in the mid-wave infrared range, managed to record a so-called secondary eclipse, when a planet passes behind its star.

In this case it was the Trappist-1b planet, the closest to the Trappist-1 star and therefore the easiest to study because its transits are larger.

“Before it disappears behind the star, the planet adds the most light (to the star’s light),” said Elsa Ducrot, an astrophysicist at the French Atomic Energy Commission (CEA), who co-authored the study, published in the journal Nature. , AFP explained.

What researchers have learned about the planet Trappist-1-b

By comparing the amount of light detected before and during the eclipse, scientists infer the amount of light emitted by the planet. It’s light that can only be detected in the mid-infrared range, a wavelength not yet used by astronomers that allows the planet’s thermal radiation to be detected.

In this way, JWST acts “like a giant non-contact thermometer,” commented astrophysicist Thomas Green, lead author of the study.

Temperature measurements on Trappist-1-b are the first for a rocky exoplanet. According to the data, the temperature on this planet is about 230 degrees Celsius on the day side, indicating that “there is no redistribution of heat across the planet, which is played by the atmosphere,” said the CEA, which developed the MIRIM instrument.

In conclusion, Trappist-1b “has little or no atmosphere,” Elsa Ducrot said, stressing that it will be necessary to look at other wavelengths to be able to confirm this with certainty.

However, if there is an atmosphere, it does not contain carbon dioxide, said the astrophysicist. The previous Spitzer telescope failed to detect these details “despite observing 28 secondary eclipses of Trappist-1b.”

“James Webb saw them in one eclipse!” said the researcher, welcoming this achievement.

A “new era” for the study of planets outside our solar system

By detecting the atmosphere around a rocky planet for the first time, the NASA-developed telescope opens a “new era” for the study of exoplanets, she added.

The planet Trappist-1b is too close to its star to support life as we know it.

However, observations made on it can provide valuable information about its “sister” planets, NASA said.

Including Trappist-1e, Trappist-1f, and Trappist-1g, which are in the habitable zone, a region that is neither too hot nor too cold to have liquid water, creating conditions conducive to alien life.

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