Webb Telescope helps measure temperature of exoplanet, 40 light years from Earth

The team employed secondary eclipse photometry to measure the change in the systems brightness as the planet moved behind the star, using MIRI.If it has an atmosphere to circulate and redistribute the heat, the dayside will be cooler than if there is no atmosphere, said Pierre-Olivier Lagage from CEA, a co-author on the paper.The infrared light being given off by the planet was calculated by subtracting the brightness of the star from the brightness of the star and planet combined.

Scientists used National Aeronautics and Space Administration's (NASA's) James Webb Space Telescope (JWST) to measure the temperature of an exoplanet TRAPPIST-1 b of an M-dwarf system 40 light years from Earth.

The measurement was close to 225 degrees Celsius and was done by detecting the planet's thermal emissions, recorded by the infrared sensor of the Webb telescope, Mid-Infrared Instrument (MIRI).

The international team of scientists involved in the study are also trying to determine if the exoplanet has an atmosphere or not, they said. The study is published in the journal Nature.

According to the study, this is an important step to determine if planets in the TRAPPIST-1 system can sustain atmospheres needed to support life, aided by Webb's ability to characterize temperate, Earth-sized exoplanets using MIRI.

TRAPPIST-1 b is the innermost planet of its system having an orbital distance one hundredth that of Earth's and receiving four times the energy from its star and is, thus, not within its system's habitable zone.

Co-author Elsa Ducrot from the French Alternative Energies and Atomic Energy Commission (CEA) in France, who was on the team that conducted earlier studies of the TRAPPIST-1 system, said, ''It's easier to characterize terrestrial planets around smaller, cooler stars. If we want to understand habitability around M stars, the TRAPPIST-1 system is a great laboratory. These are the best targets we have for looking at the atmospheres of rocky planets.'' To detect if the TRAPPIST-1 b possessed any atmosphere, the scientists measured the planet's temperature. The team employed secondary eclipse photometry to measure the change in the system's brightness as the planet moved behind the star, using MIRI.

''If it has an atmosphere to circulate and redistribute the heat, the dayside will be cooler than if there is no atmosphere,'' said Pierre-Olivier Lagage from CEA, a co-author on the paper.

The infrared light being given off by the planet was calculated by subtracting the brightness of the star from the brightness of the star and planet combined. The planet is not hot enough to give off visible light of its own.

The team analysed data from five separate secondary eclipse observations.

''We compared the results to computer models showing what the temperature should be in different scenarios,'' explained Ducrot.

''The results are almost perfectly consistent with a blackbody made of bare rock and no atmosphere to circulate the heat. We also didn't see any signs of light being absorbed by carbon dioxide, which would be apparent in these measurements,'' said Ducrot.

The team hopes to eventually establish a full phase curve, conveying the brightness change over the entire orbit.

Recording the temperature changes from day to the nightside will help the scientists, in confirming if the planet has an atmosphere or not, they said.

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