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Showing just how precise it can be, the James Webb Space Telescope detects the first definitive signature of carbon dioxide in an exoplanet atmosphere.
Illustration showing what the exoplanet WASP-39 b could look like, based on current understanding of the planet. (Credit: NASA/ESA/CSA/J. Olmsted) In a remarkable demonstration of its accuracy and precision, the James Webb Space Telescope (JWST), a collaboration between NASA, the European Space Agency and the Canadian Space Agency, has captured definitive evidence of carbon dioxide in the atmosphere of a gas giant planet . orbiting a Sun-like star 700 light-years away. The result, which has been accepted for publication in Nature, provides important information about the composition and formation of the exoplanet and is indicative of Webb’s ability to detect and measure carbon dioxide in the thinner atmospheres of smaller rocky planets. And beyond that, a better understanding of such exoplanets could lead to finding worlds that could host alien life. The team that made the discovery got time at the telescope through an Early Release Science program, which was chosen to collect some of Webb’s first data after it began science work in late June Led by Natalie Batalha of the University of California Santa Cruz, the team includes astronomers from around the world, including Björn Benneke of the Université de Montréal, who is also a member of the Institute for Research on Exoplanets (iREx). The target of the observing program, WASP-39 b, is a hot gas giant planet with a mass about a quarter that of Jupiter (about the same as Saturn) and a diameter 1.3 times that of Jupiter. Its extreme swelling is partly related to its high temperature (about 900°C). Unlike the cooler, more compact gas giants in our Solar System, WASP-39 b orbits very close to its star — only about one-eighth the distance between the Sun and Mercury — completing an orbit in just over four Earth days. The discovery of the planet, reported in 2011, was based on ground-based detections of the subtle, periodic dimming of light from its host star as the planet transits or passes in front of the star. During a transit, some of the starlight is completely blocked by the planet (causing total dimming) and some passes through the planet’s atmosphere. Because different gases absorb different combinations of colors, researchers can analyze small differences in the brightness of emitted light across a spectrum of wavelengths to determine exactly what an atmosphere is made of. With its combination of inflated atmosphere and frequent transits, WASP-39 b is an ideal target for transmission spectroscopy. The team used Webb’s (NIRSpec) to make this detection.

First clear detection of CO2

A transmission spectrum of the hot gas giant exoplanet WASP-39 b recorded by Webb’s (NIRSpec) July 10, 2022, reveals the first definitive evidence for carbon dioxide on a planet outside the Solar System. (Credit: NASA/ESA/CSA/L. Hustak/J. Olmsted/STScI) What the discovery team saw was extremely impressive. An important signal – an absorption feature – was detected at wavelengths between 4.1 and 4.6 microns in the infrared. It is the first clear, detailed, indisputable evidence for carbon dioxide ever detected on a planet outside the Solar System. “I was completely surprised,” said Benneke, professor of physics at UdeM and member of the transiting exoplanet team, who worked on the conception of the observing program and the analysis of the NIRSpec data with UdeM Louis-Philippe Coulombe graduate students Caroline Piaulet. , Michael Radica, and Pierre-Alexis Roy and postdoctoral researcher Jake Taylor. “We analyzed the data here in Montreal and we saw this huge huge signature of carbon dioxide: 26 times stronger than any noise in the data. Before the JWST, we often dug the noise, but here we had a perfectly solid signature. It’s like seeing something clearly with your own eyes.” Björn Benneke, professor at Université de Montréal and iREx, is a key member of the team that discovered the first definitive signature of carbon dioxide in an exoplanet atmosphere. (Credit: Amélie Philibert) No observatory has ever before measured such subtle differences in the brightness of so many individual infrared colors in an exoplanet transmission spectrum. Access to this part of the spectrum, from 3 to 5.5 microns, is crucial for measuring the abundance of gases such as water and methane, as well as carbon dioxide, which are believed to exist in many different types of exoplanets. “The detection of such a clear carbon dioxide signal in WASP-39 b bodes well for detecting atmospheres on smaller Earth-sized planets,” said Batalha, the program’s principal investigator. “On Earth,” Benneke added, “carbon dioxide plays such an important role in our climate, and we’re used to seeing its spectroscopic signatures here. Now, we see that signature on a distant world. This really drives home the message that these exoplanets are real worlds: as real as Earth and the planets in our Solar System.” The James Webb Space Telescope is the world’s premier space science observatory. Webb will solve mysteries in our solar system, look beyond distant worlds around other stars, and explore the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners ESA (European Space Agency) and the Canadian Space Agency. About this study “Identification of carbon dioxide in an exoplanet atmosphere,” by the JWST Transiting Exoplanet Community Early Release Science Group, was published online on arXiv today and will be published September 1, 2022 in Nature. For more information press release NASA/STScIarXiv preprint of the scientific paper Scientific ContactBjörn Benneke Professor Institute for Research on Exoplanets, University of Montreal Email: [email protected]: 514-578-2716 Media Contact Nathalie OuelletteWebb Outreach ScientistInstitute for Research on Exoplanets, University of MontrealEmail: [email protected]: 613-531-1762

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