James Webb uncovers the mysteries of an alien world's atmosphere 700 light-years away

"We are going to be able to see the big picture of exoplanet atmospheres."
Chris Young
An artist's impression of WASP-39 b.
An artist's impression of WASP-39 b.

NASA, ESA, CSA, Joseph Olmsted (STScI) 

NASA's James Webb Space Telescope has provided a detailed molecular and chemical profile of a distant exoplanet's skies in a world first, a blog post from the space agency reveals.

The planet — an exoplanet as it is located outside of our solar system — is called WASP-39 b, and it has been observed before by many telescopes, including NASA's Hubble and Spitzer.

However, the new observations from James Webb reveal the makeup of the exoplanet's atmosphere like never before and reveal further details of active chemistry and clouds.

Investigating an alien world

James Webb's state-of-the-art instruments were trained on the atmosphere of WASP-39b, a "hot Saturn" planet orbiting a star roughly 700 light-years away. The investigation shows off the $10 billion space observatory's capacity for investigating alien worlds and suggests that many more exciting findings are to come over the next decade or so of its scientific operations.

"We are going to be able to see the big picture of exoplanet atmospheres," Laura Flagg, a researcher at Cornell University and a member of the international team working on the investigation, said in NASA's post. "It is incredibly exciting to know that everything is going to be rewritten. That is one of the best parts of being a scientist."

The discoveries are detailed in five new scientific papers, two of which are still under review. One of these papers outlines the world-first detection of sulfur dioxide (SO2) in an exoplanet atmosphere. The SO2 molecules are produced by chemical reactions triggered by high-energy light from the planet's host star in a similar fashion to the ozone layer on Earth.

"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."

Scientists also applied these findings to computer models of photochemistry, which could improve the scientific community's capacity for detecting signs of habitability on distant planets.

"This is the first time we see concrete evidence of photochemistry – chemical reactions initiated by energetic stellar light – on exoplanets," added 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]."

The new data also sheds new light on how the clouds of WASP-39 b might look up close, suggesting they are broken up in the same way as the clouds on Earth instead of forming a single, uniform blanket across the exoplanet's skies.

Uncovering the mysteries of WASP-39 b

James Webb took readings of WASP-39 b when the planet passed before its host star. This allowed some of the star's light to pass through the exoplanet's atmosphere, allowing James Webb to take spectroscopy readings with its highly-sensitive instruments.

Different chemicals in the atmosphere absorb different colors of the starlight spectrum, allowing astronomers to determine which molecules are present. As NASA explains in its blog post, James Webb's infrared observation instruments will enable the observatory to "pick up chemical fingerprints that can’t be detected in visible light."

James Webb also detected sodium (Na), potassium (K), carbon dioxide (CO2), carbon monoxide (CO), and water vapor (H2O) in the exoplanet's atmosphere.

James Webb uncovers the mysteries of an alien world's atmosphere 700 light-years away
Readings from James Webb's observations of WASP 39-b.

“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.

These readings provide several clues about the evolution of WASP-39 b. For one, scientists believe that oxygen is more abundant than carbon in the atmosphere, indicating that WASP-39 b originally formed far from its host star. The abundance of sulfur on the planet, when compared with the relative lack of hydrogen, also suggests the planet "experienced significant accretion of planetesimals that can deliver [these ingredients] to the atmosphere,” according to Kazumasa Ohno, a UC Santa Cruz exoplanet researcher who worked on Webb data.

NASA says James Webb's first exoplanet readings have far exceeded expectations. The space observatory is expected to remain operational for approximately 10 years, during which it will uncover the mysteries of countless other alien worlds.

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