Jasmina Blecic, a scientist from the Center for Astro, Particle and Planetary Physics (CAP3) at New York University Abu Dhabi (NYUAD), is a member of the James Webb Space Telescope (JWST) Transiting Exoplanet Community Early Release Science team, whose joint efforts led to the first unequivocal detection of carbon dioxide in a planetary atmosphere outside our solar system. This finding was published online, and will appear in the journal Nature.
NASA’s James Webb Space Telescope has captured an astonishingly detailed rainbow of near-infrared starlight filtered through the atmosphere of a hot gas giant 700 light-years away. The transmission spectrum of exoplanet WASP-39 b, based on a single set of measurements made using Webb’s Near-Infrared Spectrograph and analyzed by dozens of scientists, represents a hat trick of firsts: Webb’s first official scientific observation of an exoplanet; the first detailed exoplanet spectrum covering this range of near-infrared colors; and the first indisputable evidence for carbon dioxide in the atmosphere of a planet orbiting a distant star. The results are indicative of Webb’s ability to spot key molecules like carbon dioxide in a wide variety of exoplanets – including smaller, cooler, rocky planets – providing insights into the composition, formation, and evolution of planets across the galaxy.
WASP-39 b is a hot gas giant with a mass roughly one-quarter that of Jupiter (about the same as Saturn) and a diameter 1.3 times greater than Jupiter. Its extreme puffiness is related in part 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 about one-eighth the distance between the Sun and Mercury – completing one circuit in just over four Earth-days. The planet’s discovery, reported in 2011, was made 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.
Previous observations from 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 unmatched 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 edge-on rather than from above, can provide researchers with ideal opportunities to probe planetary atmospheres. During a transit, some of the starlight is eclipsed by the planet completely (causing the overall dimming) and some is transmitted through the planet’s atmosphere. Blecic, along with Ian Dobbs-Dixon, the PI of the Exoplanet Research group at NYUAD, specialize in using these transit observations to unveil the multitude of secrets hidden inside the exoplanetary atmospheres: their temperatures, compositions, dynamics, and clouds. The atmospheric chemical structure is of their particular interest. Because different gases absorb different combinations of colors, one is able to analyze small differences in brightness of the transmitted light across a spectrum of wavelengths to determine exactly what an atmosphere is made of.
In the case of WASP-39 b, the combination of its inflated atmosphere and frequent transits, made it an ideal target for transmission spectroscopy, prompting it to be chosen for observations during the first months after the JWST launch. The research team used Webb’s Near-Infrared Spectrograph (NIRSpec) for its observations of WASP-39b. In the resulting spectrum of the exoplanet’s atmosphere, a small hill between 4.1 and 4.6 microns presents the first clear, detailed evidence for carbon dioxide ever detected in a planet outside the solar system. No observatory has ever measured such subtle differences in brightness of so many individual colors across the 3 to 5.5-micron range in an exoplanet transmission spectrum before.
“Detecting such a clear signal of carbon dioxide on WASP-39 b bodes well for the detection of atmospheres on smaller, terrestrial-sized planets."
“Carbon dioxide molecules are sensitive tracers of the story of planet formation,” said Mike Line of Arizona State University, another member of this research team.
This NIRSpec prism observation of WASP-39 b is just one part of a larger investigation that includes observations of the planet using multiple Webb instruments, as well as observations of two other transiting planets. Blecic is a co-investigator on all of these projects and is actively involved in modeling their atmospheres.
The investigation, which is part of the Early Release Science program, was designed to provide the exoplanet research community with robust Webb data as soon as possible. “The goal is to analyze the Early Release Science observations quickly and develop open-source tools for the science community to use,” explained Vivien Parmentier, also a co-investigator from Oxford University. “This enables contributions from all over the world and ensures that the best possible science will come out of the coming decades of observations.”
Blecic, together with Dobbs-Dixon and Mohamad Ali-Dib, a research scientist at NYUAD and a co-investigator on another JWST proposal, are currently developing comprehensive atmospheric models to analyze exoplanetary atmospheres in multidimensions utilizing JWST observations. Their models are first in the exoplanetary community that combine intrinsic physical principles and JWST observations with advanced machine learning techniques and GPU architecture to get insight into the complex 3D atmospheric structure. These state-of-the-art models would not achieve their full potential without the high resolution and wavelength coverage of the observations that have only become available with JWST.
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 probe 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.