First cloudless, Jupiter-like planet discovered

It completes a rotation around its star in just four-and-a-half days.


Astronomers at the Center for Astrophysics | Harvard & Smithsonian have detected the first Jupiter-like planet, named WASP-62b. The planet was detected without clouds or haze in its observable atmosphere.

The planet WASP-62b is also known as hot Jupiter that lies about 575 light-years away. It has half the mass of our solar system’s Jupiter. However, unlike our Jupiter, which takes nearly 12 years to orbit the sun, WASP-62b completes a rotation around its star in just four-and-a-half days. This proximity to the star makes it extremely hot, hence the name “hot Jupiter.”

Munazza Alam, a graduate student at the Center for Astrophysics who led the study, said, “For my thesis, I have been working on exoplanet characterization. I take discovered planets, and I follow up on them to characterize their atmospheres.”

Using the Hubble Space Telescope, Alam recorded data and observations of the planet using spectroscopy. Alam explicitly checked WASP-62b as it swept in front of its host star three times, making visible-light observations, which can recognize the presence of sodium and potassium in a planet’s atmosphere.

Alam said, “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.”

“While there was no evidence of potassium, sodium’s presence was strikingly clear. The team was 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.”

“This is smoking-gun evidence that we see a clear atmosphere.”

Cloud-free planets are exceedingly rare. Their rarity suggests something else is going on, or they formed differently from most planets.

Less than 7 percent of exoplanets have clear atmospheres. And according to astronomers, studying exoplanets with cloudless atmospheres can lead to a better understanding of how they were formed.

With the James Webb Space Telescope launch later this year, the team hopes to have new opportunities to study and better understand WASP-62b.

Journal Reference:
  1. Munazza K. Alam et al., Evidence of a Clear Atmosphere for WASP-62b: The Only Known Transiting Gas Giant in the JWST Continuous Viewing Zone, The Astrophysical Journal (2021). DOI: 10.3847/2041-8213/abd18e
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