A transiting gas giant called WASP-62b has a cloud- and haze-free atmosphere, according to new research.
An artist’s illustration of the hot-Jupiter WASP-62b. Image credit: M. Weiss / Harvard & Smithsonian Center for Astrophysics.
Cloud-free exoplanets are exceedingly rare; astronomers estimate that less than 7% of exoplanets have clear atmospheres.
For example, the first and only other known exoplanet with a clear atmosphere, WASP-96b, was discovered in 2018.
Astronomers believe studying exoplanets with cloudless atmospheres can lead to a better understanding of how they were formed.
“Their rarity suggests something else is going on or they formed in a different way than most planets,” said Munazza Alam, an astronomer at the Harvard & Smithsonian Center for Astrophysics.
“Clear atmospheres also make it easier to study the chemical composition of planets, which can help identify what a planet is made of.”
WASP-62b was first detected in 2012 through the Wide Angle Search for Planets (WASP) South survey.
The planet orbits WASP-62, an F-type star located 575 light-years away in the constellation of Dorado.
The alien world is about half the mass of Jupiter, and orbits its host star once every 4.4 days at a distance of 0.06 AU.
Using the NASA/ESA Hubble Space Telescope, Alam and colleagues recorded data and observations of WASP-62b using spectroscopy, the study of electromagnetic radiation to help detect chemical elements.
The astronomers specifically monitored the planet as it swept in front of its host star three times, making visible light observations, which can detect the presence of sodium and potassium in a planet’s atmosphere.
“I’ll admit that at first I wasn’t too excited about this planet. But once I started to take a look at the data, I got excited,” Alam said.
While there was no evidence of potassium, sodium’s presence was strikingly clear.
The researchers were able to view the full sodium absorption lines in their data, or its complete fingerprint.
“Clouds or haze in the atmosphere would obscure the complete signature of sodium, and astronomers usually can only make out small hints of its presence,” Alam said.
“This is smoking gun evidence that we are seeing a clear atmosphere.”
The study was published in the Astrophysical Journal Letters.
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Munazza K. Alam et al. 2021. Evidence of a Clear Atmosphere for WASP-62b: The Only Known Transiting Gas Giant in the JWST Continuous Viewing Zone. ApJL 906, L10; doi: 10.3847/2041-8213/abd18e
