James Webb sheds light on exoplanets’ ability to support life

Researchers used the James Webb Space Telescope to measure the temperature of the deepest planet in the TRAPPIST-1 system, shedding more light on the life-supporting abilities of such planets.

TRAPPIST-1 It is an ultra-cold red dwarf star (or M-dwarf) slightly larger than Jupiter, about 40 light-years away, and orbited by seven Earth-sized exoplanets. It is about twice as old as our solar system, making it ideal for studying the formation and evolution of terrestrial planets.

The innermost of the system’s known rocky exoplanets, TRAPPIST-1b is slightly larger than Earth but has the same density. Although not in the system’s “habitable zone” like planets e, f, and g, it can still provide important information about other planets and other M-dwarf systems in the TRAPPIST-1 system.

An international team of researchers used NASA’s James Webb Space Telescope (JWST) to take a closer look at TRAPPIST-1 b to determine if the planet has an atmosphere to apply the knowledge to the habitability of other exoplanets.

“The TRAPPIST-1 system is an excellent laboratory if we want to understand the possibility of habitability around M stars,” said study co-author Elsa Ducrot. “These are the best objects we have for studying the atmospheres of rocky planets.”

One of the factors that determines a planet’s suitability for life is the presence of an atmosphere. Previous observations of TRAPPIST-1 b using the Hubble and Spitzer Space Telescopes found no evidence of a much larger-than-expected loose atmosphere, but the presence of a dense atmosphere could not be ruled out. Searching for an answer to the question about the atmosphere, the research team measured the temperature of the planet.

“This planet is tidally locked, with one side always facing the star and the other side in perpetual darkness,” said Pierre-Olivier Lagage, one of the study’s authors. “If it has an atmosphere to circulate and redistribute heat, it will be colder during the day than it is without an atmosphere.”

Because TRAPPIST-1b is not hot enough, it does not emit its own visible light, but emits an infrared glow. Using JWST’s Mid-Infrared Instrument (MIRI), the researchers were able to calculate the amount of heat emitted by the planet in the form of infrared light.

“These observations really take advantage of Webb’s mid-infrared capability,” said Thomas Green, the study’s lead author. “No previous telescope had the sensitivity to measure such weak mid-infrared light.”

They found that TRAPPIST-1 b has a daytime temperature of about 500 Kelvin (about 450°F or 227°C), suggesting that the planet has little or no atmosphere.

This is the first time researchers have been able to detect any form of light emitted by an exoplanet as small and cold as the rocky planets in our solar system. For the research team, this is an important step towards exploring whether planets in the TRAPPIST-1 system and other planets like them support life-supporting atmospheres.

Researchers have reached another important milestone: the detection of a secondary eclipse. During the secondary eclipse, the planet passes behind the star, blocking the light from the planet. MIRI measured the change in brightness from the system as TRAPPIST-1 b passed behind the star.

Data from five separate secondary eclipses were analyzed and compared with computer models showing what the temperature should have been in different scenarios.

“The results are almost perfectly consistent with a black body made of bare rock and the lack of atmosphere to circulate the heat,” Ducrot said. Said. “We also did not see any evidence of light absorption by carbon dioxide, which may be evident in these measurements.”

A black body is an object that absorbs all the radiation falling on it. It does not reflect or transmit the light and does not allow the light to pass through and exit from the other side. The energy absorbed by the blackbody heats it and causes it to emit its own radiation. The only parameter that determines how much light a blackbody will emit is temperature.

Now that the researchers have successfully captured the second eclipse, they are using JWST’s MIRI to obtain additional observations of the phenomenon, hoping to capture a full phase curve that shows the change in brightness in the planet’s orbit. This will allow researchers to compare temperature changes between the day and night sides and confirm the existence of an atmosphere.

“This is the first time we’ve been able to detect radiation from a rocky, temperate planet,” Lage said. “This is a really important step in the history of the discovery of exoplanets.”