NASA’s Webb Reveals an Exoplanet Atmosphere as Never Seen Before

NASA’s James Webb Space Telescope just scored another first: a molecular and chemical profile of a distant world’s skies.

While Webb and other space telescopes, including NASA’s Hubble and Spitzer, previously have revealed isolated ingredients of this broiling planet’s atmosphere, the new readings from Webb provide a full menu of atoms, molecules, and even signs of active chemistry and clouds.

The latest data also gives a hint of how these clouds might look up close: broken up rather than a single, uniform blanket over the planet.

The telescope’s array of highly sensitive instruments was trained on the atmosphere of WASP-39 b, a “hot Saturn” (a planet about as massive as Saturn but in an orbit tighter than Mercury) orbiting a star some 700 light-years away.

The findings bode well for the capability of Webb’s instruments to conduct the broad range of investigations of all types of exoplanets – planets around other stars – hoped for by the science community. That includes probing the atmospheres of smaller, rocky planets like those in the TRAPPIST-1 system.

“We observed the exoplanet with multiple instruments that, together, provide a broad swath of the infrared spectrum and a panoply of chemical fingerprints inaccessible until [this mission],” said Natalie Batalha, an astronomer at the University of California, Santa Cruz, who contributed to and helped coordinate the new research. “Data like these are a game changer.”

The suite of discoveries is detailed in a set of five new scientific papers, three of which are in press and two of which are under review. Among the unprecedented revelations is the first detection in an exoplanet atmosphere of sulfur dioxide (SO2), a molecule produced from chemical reactions triggered by high-energy light from the planet’s parent star. On Earth, the protective ozone layer in the upper atmosphere is created in a similar way.

“This is the first time we see concrete evidence of photochemistry – chemical reactions initiated by energetic stellar light – on exoplanets,” said Shang-Min Tsai, a researcher at the University of Oxford in the United Kingdom and lead author of the paper explaining the origin of sulfur dioxide in WASP-39 b’s atmosphere. “I see this as a really promising outlook for advancing our understanding of exoplanet atmospheres with [this mission].”

This led to another first: scientists applying computer models of photochemistry to data that requires such physics to be fully explained. The resulting improvements in modeling will help build the technological know-how to interpret potential signs of habitability in the future.

“Planets are sculpted and transformed by orbiting within the radiation bath of the host star,” Batalha said. “On Earth, those transformations allow life to thrive.”

The planet’s proximity to its host star – eight times closer than Mercury is to our Sun – also makes it a laboratory for studying the effects of radiation from host stars on exoplanets. Better knowledge of the star-planet connection should bring a deeper understanding of how these processes affect the diversity of planets observed in the galaxy.

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To see light from WASP-39 b, Webb tracked the planet as it passed in front of its star, allowing some of the star’s light to filter through the planet’s atmosphere. Different types of chemicals in the atmosphere absorb different colors of the starlight spectrum, so the colors that are missing tell astronomers which molecules are present. By viewing the universe in infrared light, Webb can pick up chemical fingerprints that can’t be detected in visible light.

Other atmospheric constituents detected by the Webb telescope include sodium (Na), potassium (K), and water vapor (H2O), confirming previous space and ground-based telescope observations as well as finding additional fingerprints of water, at these longer wavelengths, that haven’t been seen before.

Webb also saw carbon dioxide (CO2) at higher resolution, providing twice as much data as reported from its previous observations. Meanwhile, carbon monoxide (CO) was detected, but obvious signatures of both methane (CH4) and hydrogen sulfide (H2S) were absent from the Webb data. If present, these molecules occur at very low levels.

To capture this broad spectrum of WASP-39 b’s atmosphere, an international team numbering in the hundreds independently analyzed data from four of the Webb telescope’s finely calibrated instrument modes.

“We had predicted what [the telescope] would show us, but it was more precise, more diverse, and more beautiful than I actually believed it would be,” said Hannah Wakeford, an astrophysicist at the University of Bristol in the United Kingdom who investigates exoplanet atmospheres.

Having such a complete roster of chemical ingredients in an exoplanet atmosphere also gives scientists a glimpse of the abundance of different elements in relation to each other, such as carbon-to-oxygen or potassium-to-oxygen ratios. That, in turn, provides insight into how this planet – and perhaps others – formed out of the disk of gas and dust surrounding the parent star in its younger years.

WASP-39 b’s chemical inventory suggests a history of smashups and mergers of smaller bodies called planetesimals to create an eventual goliath of a planet.

“The abundance of sulfur [relative to] hydrogen indicated that the planet presumably experienced significant accretion of planetesimals that can deliver [these ingredients] to the atmosphere,” said Kazumasa Ohno, a UC Santa Cruz exoplanet researcher who worked on Webb data. “The data also indicates that the oxygen is a lot more abundant than the carbon in the atmosphere. This potentially indicates that WASP-39 b originally formed far away from the central star.”

In so precisely parsing an exoplanet atmosphere, the Webb telescope’s instruments performed well beyond scientists’ expectations – and promise a new phase of exploration among the broad variety of exoplanets in the galaxy.

“We are going to be able to see the big picture of exoplanet atmospheres,” said Laura Flagg, a researcher at Cornell University and a member of the international team. “It is incredibly exciting to know that everything is going to be rewritten. That is one of the best parts of being a scientist.”

https://www.nasa.gov/feature/goddard/2022/nasa-s-webb-reveals-an-exoplanet-atmosphere-as-never-seen-before

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Hubble Glimpses a Glittering Gathering of Stars

This glittering gathering of stars is Pismis 26, a globular star cluster located about 23,000 light-years away. Many thousands of stars gleam brightly against the black backdrop of the image, with some brighter red and blue stars located along the outskirts of the cluster. The Armenian astronomer Paris Pismis first discovered the cluster in 1959 at the Tonantzintla Observatory in Mexico, granting it the dual name Tonantzintla 2.

Pismis 26 is located in the constellation Scorpius near the galactic bulge, which is an area near the center of our galaxy that holds a dense, spheroidal grouping of stars that surrounds a black hole. Due to its location within the dust-heavy bulge, a process called “reddening” occurs, where dust scatters shorter wavelength blue light while longer wavelength red light passes through. Reddening distorts the apparent color of cosmic objects. Globular clusters are groups of stars held together by mutual gravitational attraction. They contain thousands of tightly packed stars and appear almost spherical in shape. Astronomers used NASA’s Hubble Space Telescope to study visible and infrared light from Pismis 26 to determine the cluster’s reddening, age, and metallicity.

The stars of Pismis 26 have high metallicity, meaning they contain a high fraction of elements heavier than hydrogen and helium, the most abundant elements in the universe. Specifically, the stars are rich in the element nitrogen, which is typical of stars in bulge clusters and has led scientists to believe that populations of differently-aged stars are present in the cluster. Pismis 26 has also likely lost a sizable portion of its mass over time due to a gravitational force called the strong inner galaxy tidal field, which the inner galaxy exerts on star clusters in the galactic bulge, causing their outer layers to pull away. Researchers estimate the age of the cluster to be 12 billion years old.

https://www.nasa.gov/image-feature/goddard/2022/hubble-glimpses-a-glittering-gathering-of-stars