Researchers used the James Webb Space Telescope to measure the temperatures of the TRAPPIST-1 system’s innermost planets, shedding more light on the ability of planets like these to sustain life.
TRAPPIST-1 is an ultracold red dwarf (or M dwarf) slightly larger than Jupiter, about 40 light-years away, orbited by seven Earth-sized exoplanets. It is up to twice as old as our own solar system, making it ideal for studying the formation and evolution of terrestrial planets.
The innermost known rocky exoplanet in the system, TRAPPIST-1 b is slightly larger than Earth, but has the same density. Although not within the “habitable zone” of systems like planets e, f, and g, it can provide important information about other planets in the TRAPPIST-1 system and planets in other M dwarf systems.
An international team of researchers will use NASA’s James Webb Space Telescope (JWST) to probe TRAPPIST-1 b and to apply the information gained to the habitability of other exoplanets. Determined if there is an atmosphere.
“The TRAPPIST-1 system is a great laboratory if we want to understand the habitability around M stars,” said study co-author Elsa Ducrot. “They are the best targets for observing the atmospheres of rocky planets.”
One of the factors that determine a planet’s habitability is the presence of an atmosphere. His previous observations of TRAPPIST-1 b using the Hubble and Spitzer Space Telescopes found no evidence of a puffy atmosphere. Seeking answers to questions about the atmosphere, the research team measured the temperature of the planet.
“The planet is tidally locked, with one side always facing the stars and the other in permanent darkness,” said Pierre-Olivier Lagage, one of the study’s authors. “If you have an atmosphere that circulates and redistributes heat, it will be cooler during the day than without it.”
TRAPPIST-1 b isn’t hot enough, so it doesn’t emit visible light itself, but it does emit an infrared glow. Using JWST’s Mid-Infrared Instrument (MIRI), researchers were able to calculate the amount of heat emitted as infrared radiation produced by the planet.
“These observations really take advantage of the web’s mid-infrared capabilities,” said Thomas Green, lead author of the study. “No previous telescope had the sensitivity to measure such dim mid-infrared light.”
They found that TRAPPIST-1 b has a dayside temperature of about 500 Kelvin (about 450 °F or 227 °C). This suggests that the planet has little or no atmosphere.
This is the first time researchers have been able to detect any form of light emitted from an exoplanet as small and cold as a rocky planet in our solar system. For the research team, this is an important step toward discovering whether planets in the TRAPPIST-1 system and such planets can sustain life-supporting atmospheres.
Another major milestone was achieved by the researchers: the detection of secondary meals. In a secondary eclipse, a planet passes behind the star, blocking the light from the planet. MIRI measured the change in brightness from the system as TRAPPIST-1 b moved behind the star.
Data from five separate secondary meals were analyzed and compared to computer models showing what temperatures should be in different scenarios.
“The result is an almost perfect match for a bare rocky blackbody with no atmosphere to circulate heat,” Ducrot said. “We also didn’t see any indication that the light was absorbed by the carbon dioxide, which is evident in these measurements.”
A blackbody is an object that absorbs all radiation that hits it. It does not reflect or transmit light, nor does it pass through to the other side. The energy that a blackbody absorbs heats it up and produces its own radiation. Temperature is the only parameter that determines how much light a blackbody emits.
Now that the secondary eclipse has been successfully imaged, the researchers will use JWST’s MIRI to obtain additional observations of the phenomenon, hoping to capture the full phase curve showing changes in brightness across the planet’s orbit. is. This allows researchers to compare temperature changes between day and night to confirm the presence of an atmosphere.
“This is the first time we have detected radiation from a rocky temperate planet. This is a very important step in the story of finding exoplanets,” Lagarge said.
The study was published in a journal Nature.
Source: NASA’s Goddard Space Flight Center
