Discovered in 2017, the seven rocky planets orbiting TRAPPIST-1, an ultracool red dwarf star, are strikingly similar in size and mass to our solar system's inner planets.
First Light Detection from a Cool, Small Exoplanet
An international research team utilized NASA’s James Webb Space Telescope to measure the temperature of TRAPPIST-1 b, a rocky exoplanet. The measurement relied on the planet’s thermal emission, detected by Webb’s Mid-Infrared Instrument (MIRI), revealing a dayside temperature of approximately 500 kelvins and suggesting the absence of a significant atmosphere.
A New Era in Exoplanet Exploration
This groundbreaking discovery marks the first detection of light emitted by an exoplanet as small and cool as those in our solar system. The results will contribute to understanding whether planets orbiting small active stars like TRAPPIST-1 can support life-sustaining atmospheres and highlight Webb’s capability to characterize Earth-sized exoplanets using MIRI.
Revolutionizing Mid-Infrared Observations
Thomas Greene, an astrophysicist at NASA’s Ames Research Center and lead author of the study, emphasized the significance of Webb’s mid-infrared capabilities, noting that no previous telescopes had the sensitivity to measure such dim mid-infrared light.
TRAPPIST-1: A Laboratory for Habitable Planets
Discovered in 2017, the seven rocky planets orbiting TRAPPIST-1, an ultracool red dwarf star, are strikingly similar in size and mass to our solar system’s inner planets. Though they orbit much closer to their star, they receive comparable amounts of energy from it. TRAPPIST-1 b, the innermost planet, offers valuable insights into its sibling planets and other M-dwarf systems.
As the nearest planet to its star, TRAPPIST-1 b’s orbit is a mere one-hundredth of Earth’s distance from the Sun, and it receives approximately four times the energy that Earth does. Although it doesn’t lie within its system’s habitable zone, examining this planet can yield crucial knowledge about its sister planets and additional M-dwarf systems.
Determining Temperature and Atmospheric Presence
To reduce uncertainty, the team measured TRAPPIST-1 b’s temperature using secondary eclipse photometry. Comparing computer models showing different scenarios concluded that the results were consistent with a bare rock and no atmosphere to circulate heat. No signs of light being absorbed by carbon dioxide were detected.
Future Observations and Discoveries
As part of Webb’s Guaranteed Time Observation (GTO) program, additional secondary eclipse observations of TRAPPIST-1 b are in progress, with the goal of capturing a full phase curve to observe temperature changes and confirm atmospheric presence. This significant step forward in exoplanet discovery showcases the potential of the Webb Telescope and MIRI.
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