Astrophysicists on Earth are no strangers to WASP-39b, an exoplanet orbiting a star about 700 light-years from Earth, though they never saw it directly. Now the Webb Space Telescope has offered new insight into this distant world: The observations have revealed the recipe list for the planet’s toxic atmosphere.
WASP-39b is a gas giant about the mass of Saturn and the size of Jupiter, but it orbits its star at about the same distance as Mercury from the sun, making the exoplanet very, very hot. The exoplanet was discovered in 2011; earlier this year, Webb telescope observations revealed carbon dioxide lurking in its atmosphere.
More molecules and chemical compounds have now been identified, including evidence of water, sulfur dioxide, carbon monoxide, sodium and potassium. The findings are reviewed before publication and now available on the preprint server arXiv.
“This is the first time we’ve seen concrete evidence of photochemistry — chemical reactions initiated by energetic stellar light — on exoplanets,” said Shang-Min Tsai, a researcher at the University of Oxford, lead author of the paper demonstrating the presence of sulfur dioxide. in the planet’s atmosphere, in a European Space Agency release. “I see this as a promising prospect for furthering our understanding of exoplanet atmospheres [this mission].”
It’s no easy feat sniffing out the chemicals floating in the atmosphere of a distant world. The nearest confirmed exoplanet is 40.9 trillion kilometers away. Still, Webb managed to discover such infinitely small molecules in WASP-39b.
Webb observed the planet by waiting for it to pass in front of its host star; when it did, the star’s light illuminated the planet from behind. Webb picked up the infrared wavelengths of that light, and scientists can deduce which chemicals are in the atmosphere based on the wavelengths of light they absorbed.
Webb’s capabilities have broader implications for understanding the diversity of exoplanets in our galaxy, in view of their potential habitability. With its extreme heat and gaseous composition, WASP-39b is certainly not hospitable to any life we know of, but it demonstrates the kind of molecular-level analysis Webb can apply to distant worlds.
“I’m looking forward to seeing what we find in the atmospheres of minor terrestrial planets,” said Mercedes López-Morales, an astronomer at the Center for Astrophysics | Harvard & Smithsonian and a co-author of the recent work, in the ESA release.
The data presented to the researchers that the chemicals in the planet’s atmosphere can be broken up into clouds, rather than evenly distributed throughout the atmosphere. And based on the relative amounts of the chemicals in the atmosphere, the researchers think WASP-39b evolved over time from a merger of planetesimals.
Although we don’t know where Webb will be turning his infrared look after that, we know that, at some point more exoplanets will be on the roll. Webb has already explored the atmospheres of rocky planets in the TRAPPIST-1 system and may return to the system in due course. You can keep track of Webb’s most recent goals here.
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