James Webb Space Telescope – already famous for its Fascinating cosmic images – did it again. For the first time, the telescope has captured clear evidence of carbon dioxide in the atmospheres of an exoplanet.
Not only does the discovery provide tantalizing clues about how this exoplanet formed, but it also heralds what will happen to Webb’s growing number of alien worlds.It was reported in a manuscript on the preprint server arXiv prior to peer review and is expected to be published in nature in the days to come. (nature‘s news team is independent of its journal team. )
Although the plotted data leading up to this discovery lacks the brilliance of Webb’s previous images — suggesting that Galaxies locked in cosmic dance, radiation clouds in stellar nursery — they still prompted Jessie Christiansen, an astronomer at NASA’s Institute for Exoplanet Science at Caltech in Pasadena, to describe them as “gorgeous.”
The map, or spectrum, reveals details about the atmosphere of exoplanet WASP-39b, which scientists call a “hot Jupiter” because it is slightly wider in diameter than Jupiter, but orbits its star farther than Mercury orbits the sun close, making it unbearably hot. The planet, more than 200 parsecs from Earth, was first discovered during ground-based observations and was later detected by NASA’s Spitzer Space Telescope, which operated from 2003 to 2020. Data from the latter suggest that WASP-39b’s atmosphere may contain carbon dioxide, but they are inconclusive.
Then there’s Weber. For more than eight hours on July 10, infrared telescopes observed the planet moving across its star’s surface. As it does, starlight travels through the planet’s atmosphere, and various molecules absorb specific wavelengths of infrared light. Astronomers wondered whether carbon dioxide would show up as a distinct signal in the spectrum. “It’s there — just jumping off the computer screen,” said Natalie Batalia, an astronomer at the University of California, Santa Cruz (UCSC), who led the Webb transiting exoplanet early release science team. Batalha) said.
Batalha is not alone. When Christiansen, who was not part of the team, saw the data, she gasped. “I was like ‘Oh, it’s there,'” she said. “We’ve hinted at it before, but this is the first time it’s really been a ‘face-slap’ detection.”
The results bolster confidence that Webb will revolutionize exoplanet research. In its first year of operation alone, the telescope was commissioned to observe 76 exoplanets, but the final number could be in the hundreds. It will peer into the atmospheres of gas giants and possibly small rocky worlds like Earth. “When I saw the signal, my first thought was ‘wow, this will work,'” Batalha said.
But the discovery of carbon dioxide itself is also impressive. “From a scientific standpoint, this is very exciting,” said Jonathan Fortney, director of the UCSC Other Worlds laboratory and co-author of the paper. To be sure, a planet like Jupiter formed from the same disk of material as its star has roughly the same chemical composition as that star. But that’s clearly not the case in our solar system, and neither is WASP-39b. The exoplanet’s strong carbon dioxide signal suggests it is rich in elements heavier than hydrogen and helium, which normally make up stars. The question is why?
“That’s where the story starts to get interesting,” Batalha said. It’s possible that when WASP-39b was young, it was bombarded by comets and asteroids that could have released heavier elements, such as carbon and oxygen. Interestingly, this exoplanet appears to contain the same amount of heavy elements as Saturn, which astronomers also believe went through a violent youth.
Or the answer could be that WASP-39b formed from material from the cold outer periphery of its planetary system and then migrated inward. At its final resting point, it snuggled up to its host star, which may have blown off some of the hydrogen in the exoplanet’s atmosphere — condensing the heavier elements, making it appear rich in carbon dioxide. Fortney, Batalha and their colleagues are currently working on four papers that will analyze Earth’s spectrum in more detail and further explore these possibilities.
“It’s like archeology,” Batalha said. “You’re trying to build a big story — you’re using the molecule itself, as a tracker for that story.”
cornerstone of life
The discovery of carbon dioxide in planetary atmospheres is a stepping stone to the detection of life beyond Earth. Of course, astronomers don’t expect WASP-39b to host life — it’s too close to its star. They didn’t even expect that Webb would definitely find life on another planet. But using Webb to detect carbon dioxide could help lay the groundwork for future discoveries.
Astronomers believe that a mixture of carbon dioxide and methane in a planet’s atmosphere could be a sign of life — a so-called biosignature. So WASP-39b’s signal is “half a good biosignature,” Christiansen said. Batalha’s team built a model that predicted the planet’s atmosphere also contained water, carbon monoxide and hydrogen sulfide — but little methane.
Ultimately, detection of life may require observatories more advanced than Webb’s. But, Batalha said, “this is a very important stage that we need to go through in order to be ready for the technology of the future”.
This article is reproduced with permission, first published August 29, 2022.