Scientists used the National Aeronautics and Space Administration’s (NASA) James Webb Space Telescope (JWST) to measure the temperature of the M-dwarf exoplanet TRAPPIST-1b 40 light-years from Earth. The measurement was close to 225 degrees Celsius and was made by detecting the planet’s thermal emissions, recorded by the Webb Telescope’s infrared sensor, the Mid-Infrared Instrument (MIRI).
The international team of scientists involved in the study is also trying to determine whether the exoplanet has an atmosphere or not. The study is published in the journal Nature.
This is an important step in determining whether the planets in the TRAPPIST-1 system can sustain the atmosphere needed to support life, with the help of Webb’s ability to characterize temperate Earth-sized exoplanets using MIRI.
TRAPPIST-1b is the innermost planet in its system, with an orbital distance one-hundredth that of Earth and receiving four times the energy of its star, and is therefore not in its system’s habitable zone.
Co-author Elsa Ducrot of the French Commission for Alternative Energies and Atomic Energy (CEA) in France, who was on the team that carried out earlier studies of the TRAPPIST-1 system, said: “It is 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 observing the atmospheres of rocky planets.”
To determine whether TRAPPIST-1 b has an atmosphere, the scientists measured the planet’s temperature. The team used secondary eclipse photometry to measure the change in brightness of the system as the planet moved behind the star, using MIRI.
CEA’s Pierre-Olivier Lagage, co-author says”If it has an atmosphere to circulate and redistribute heat, the dayside will be cooler than if there was no atmosphere”.
The infrared light emitted by the planet was calculated by subtracting the brightness of the star from the combined brightness of the star and planet. The planet is not hot enough to emit its own visible light. The team analyzed data from five separate secondary observations of the eclipse.
Ducrot explained ”We compared the results with computer models showing what the temperature should be in different scenarios, results are almost perfectly consistent with a black body made of bare rock and no atmosphere to circulate the heat. We also saw no sign of light absorption by carbon dioxide, which would be apparent in these measurements”.
The team hopes to eventually create a full phase curve that transmits the change in brightness across the entire orbit. Recording temperature changes from day to night will help scientists confirm whether the planet has an atmosphere or not, they said.
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