Carbon dioxide discovery on exoplanets: UAE scientists team behind astronomical breakthrough

NASA’s James Webb Space Telescope has captured a stunningly detailed rainbow of near-infrared starlight filtered from the atmosphere of a hot gas giant star 700 light-years away. The transmission spectrum of the exoplanet WASP-39 b, based on a set of measurements made with the Webb near-infrared spectrometer and analyzed by dozens of scientists, represents a first-of-its-kind hat-trick: Webb’s first official scientific observation of an exoplanet; the first Detailed exoplanet spectra covering this near-infrared color range; and the first indisputable evidence for the presence of carbon dioxide in the atmospheres of planets orbiting distant stars. The results demonstrate Webb’s ability to find key molecules such as carbon dioxide in a variety of exoplanets, including smaller, cooler, rockier ones, and provide insights into the composition, formation and evolution of planets across the galaxy.

WASP-39 b is a hot gas giant about a quarter the mass of Jupiter (about the same as Saturn) and 1.3 times the diameter of Jupiter. Part of its extreme puffiness is related to its high temperature (about 1,600 degrees Fahrenheit or 900 degrees Celsius). Unlike the cooler, more compact gas giants in our solar system, WASP-39 b orbits very close to its star — only one-eighth the distance between the sun and Mercury — and completes one lap in four Earth days . The discovery of the planet, reported in 2011, is based on ground-based detections of subtle, periodically dimming light from its host star as the planet transits or passes in front of the star.

Previous observations by other telescopes, including NASA’s Hubble and Spitzer Space Telescopes, revealed the presence of water vapor, sodium and potassium in the planet’s atmosphere. Webb’s unparalleled infrared sensitivity has now confirmed the presence of carbon dioxide on this planet as well.

Transiting planets like WASP-39 b, whose orbits we observe from the side rather than from above, can provide researchers with the ideal opportunity to probe the planet’s atmosphere. During the transit, some starlight is completely obscured by the planet (causing an overall dimming), and some starlight travels through the planet’s atmosphere.

Along with Ian Dobbs-Dixon, principal investigator of the NYU Exoplanet Research Group, Blecic used these transit observations specifically to reveal the many secrets hidden in exoplanet atmospheres: their temperature, composition, dynamics and clouds. The chemical structure of the atmosphere is of particular interest to them. Because different gases absorb different color combinations, one can accurately determine the composition of the atmosphere by analyzing small differences in the brightness of transmitted light across the entire wavelength range.

In the case of WASP-39 b, the combination of its expanding atmosphere and frequent transits made it an ideal target for transmission spectroscopy, prompting its selection for observations in the first few months after the JWST launch. The research team used Webb’s near-infrared spectrometer (NIRSpec) to observe WASP-39b. A small hill between 4.1 and 4.6 microns in the spectrum of the exoplanet’s atmosphere provides the first clear, detailed evidence of carbon dioxide detected in an exoplanet. No observatory has previously measured such subtle differences in brightness for so many colors in the 3 to 5.5 micrometer range in exoplanet transmission spectra.

The detection of such a clear carbon dioxide signal on WASP-39 b bodes well for detecting atmospheres on smaller terrestrial planets,” said team leader Natalie Bataha of the University of California, Santa Cruz. .

“Carbon dioxide molecules are sensitive tracers for the planet formation story,” said Mike Lane of Arizona State University, another member of the research team.

The NIRSpec prism observations of WASP-39 b are just part of a larger survey that includes observations of the planet using multiple Webb instruments, as well as observations of two other transiting planets. Blecic is a co-researcher on all of these projects and is actively involved in simulating their atmospheres.

The survey is part of an Early Release Science initiative to provide the exoplanet research community with robust Webb data as soon as possible.

“Our goal is to rapidly analyze early published scientific observations and develop open-source tools for use by the scientific community,” explains co-researcher Vivien Parmentier from the University of Oxford.

“This enables contributions from around the world and ensures that the best science is produced in the coming decades of observations,” she added.

Blecic, along with Dobbs-Dixon and Mohamad Ali-Dib, a NYU research scientist and co-investigator on another JWST proposal, are currently developing a comprehensive atmospheric model to analyze multidimensional exoplanet atmospheres using JWST observations. Their model, the first in the exoplanet community, combines intrinsic physical principles and JWST observations with advanced machine learning techniques and GPU architecture to gain insight into complex 3D atmospheric structures. These state-of-the-art models would not be able to reach their full potential without the high-resolution and wavelength-covered observations available only at JWST.

The James Webb Space Telescope is the world’s premier space science observatory. Webb will unravel the mysteries of our solar system, move beyond distant worlds around other stars, and explore the mysterious structure and origins of our universe and our place in it. Webb is an international initiative led by NASA and its partners ESA (European Space Agency) and the Canadian Space Agency.