Illustration of exoplanet WASP-39 b and its star (NASA) | SkyNews
Illustration of exoplanet WASP-39 b and its star (NASA)

JWST explores atmosphere of ‘hot Saturn’ exoplanet

WASP-39 b has sulfur dioxide; sodium, potassium, water vapour, and carbon monoxide were also detected in the atmosphere.

Astronomers using the James Webb Space Telescope now know the atmospheric portrait of a planet 700 light years away in the constellation Virgo —a scientific first that demonstrates Webb can make similar observations of other exoplanets.

The observations were made by an international group of astronomers, which included a team at the Université de Montréal in Québec. Webb’s Canadian-designed NIRISS instrument (Near Infrared Imager and Slitless Spectrograph) played a crucial role in observing the planet. 

“We can now start pushing JWST and NIRISS’s capabilities even further,” said Michael Radica, a UdeM doctoral student, in a statement from the university. “The lessons learned from the Early Release Science observations are already proving invaluable with analyses of smaller Neptune- and even Earth-sized planets currently in the works.”

The exoplanet is a gas giant called WASP-39 b. It is considered a “hot Saturn,” meaning it is roughly the size of Saturn, and orbits its sun eight times closer than Mercury orbits our Sun.

The findings have been recorded in five new scientific papers, three of which are in press and two of which are being reviewed. But the data collected so far is unprecedented in exoplanet research.

WASP-39 b has sulfur dioxide, a compound created through chemical reactions caused by ultraviolet light from the planet’s star. The ozone layer over Earth is created through a similar reaction. The process, known as photochemistry, has never been seen outside our Solar System until now.

The team also detected sodium, potassium, water vapour, and carbon monoxide in the atmosphere. Methane and hydrogen sulfide were not detected, meaning those compounds exist at low levels if they exist at all. The same researchers involved also announced last August that WASP-39 b had carbon dioxide. 

The data suggests the planet’s clouds are broken up rather than a single, uniform blanket covering the planet. The close orbit also makes WASP-39 b an ideal candidate for studying radiation from host stars on exoplanets.

“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, in a NASA statement. “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 atmospheric composition of WASP-39 b | SkyNews
The atmospheric composition of WASP-39 b (NASA, ESA, CSA, J. Olmsted (STScI))

Get a Free Digital Issue