The James Webb Space Telescope (JWST) has had its first glimpse of a long-awaited set of targets – the atmospheres of some of the seven Earth-sized planets surrounding the star TRAPPIST-1, just 12 parsecs (39 years) away. -light) of the Earth. All seven are in or near their star’s habitable zone, where liquid water could exist, and astronomers consider them the best-known laboratory for studying what makes planets beyond the solar system conducive to life.
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What researchers have seen so far is preliminary and does not yet indicate what sorts of atmospheres these planets might actually have. But if they have atmospheres dense with intriguing molecules such as carbon dioxide or methane, the $10 billion telescope will be able to detect them in the months and years to come. No other observatory has been powerful enough to spot these atmospheres.
“We’re in business,” Björn Benneke, an astronomer at the University of Montreal, said at a symposium on early JWST results in Baltimore, Maryland, Dec. 13.
The TRAPPIST-1 planetary system, mapped in 2017, offers astronomers multiple chances to understand the formation and evolution of Earth-sized worlds around a single star. The star is relatively faint and cool, and the seven planets are nestled closer to it than Mercury orbits the Sun.
JWST observes all the planets in its first year of science operations, which began in June. Many of these observations have already been taken, but none had been shown publicly until this week’s symposium, which took place at the Space Telescope Science Institute, JWST’s operations center.
The TRAPPIST-1 planets are labeled b through h, with b being closest to the star and h being farthest.
Benneke showed the first JWST studies of TRAPPIST-1g. So far, the telescope has been able to determine that it probably doesn’t have a hydrogen-rich atmosphere, which would be relatively easy to spot because it’s physically so large. This could mean that the planet has a denser atmosphere, made up of heavier molecules, such as carbon dioxide, or no atmosphere at all.
JWST studies planetary atmospheres primarily by observing how they filter starlight passing through them as they pass in front of the star. The molecules that make up a planet’s atmosphere can tell how it evolved and whether it might have life on its surface. It will take even more observations and time to analyze the data collected so far, before researchers know if TRAPPIST-1g has an atmosphere, and if so what it is made of.
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TRAPPIST-1 data is much harder to analyze than data collected from larger exoplanets, including WASP-39b, a planet closer to the size of Jupiter that JWST has studied in detail. TRAPPIST-1’s planets are much smaller and the signal from their atmospheres harder to disentangle. Magnetic disturbances in TRAPPIST-1 can also induce signals that confuse data interpretations.
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“We needed that first look to know what we’re dealing with,” says Knicole Colón, an astronomer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who was not involved in the work. Benneke declined to speak to reporters about the TRAPPIST-1g results, citing an article under review in a scientific journal.
In a poster presentation at the conference, Olivia Lim from the University of Montreal showed two JWST observations of the system’s innermost planet, TRAPPIST-1b. She too has not yet been able to pick up a signal indicating the planet’s atmosphere. But preliminary studies suggest that, like Planet 1g, it probably doesn’t have a puffy, hydrogen-rich atmosphere.
Lim has several other observations of other TRAPPIST-1 planets already underway, including one taken last week that she hasn’t had time to look at yet in the rush of JWST results. “It’s hectic,” she said.
But more findings on the extraordinary planetary system are on the way, says Colón: “During the next year, we will have a family portrait.
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