Astronomers discover the first cloudless planet, similar to Jupiter

Astronomers at the Astrophysics Center Harvard & Smithsonian have discovered the first Jupiter-like planet with no clouds or fog in the visible atmosphere. The results were published this month in the Astrophysical Journal Letters.

Named WASP-62b, the gas giant was first discovered in 2012 through the Southern Wide Angle Search for Planets (WASP) study. However, the atmosphere has not been closely studied to date.

“For my dissertation, I have been working on an exoplanet character,” said Munazza Alam, a graduate student at the Astrophysics Center who led the study. “I take out planets and I continue to identify them with their emotions.”

Known as “Hot Jupiter,” the WASP-62b is 575 light years away and about half the Jupiter mass of our solar system. However, unlike our Jupiter, which takes nearly 12 years to orbit the sun, WASP-62b completes orbiting its star in just four and a half days. The proximity of the star makes it incredibly hot, hence the name “hot Jupiter.”

Using the Hubble Space Telescope, Alam recorded data and observations on the planet using spectroscopy, the study of electromagnetic radiation to help detect chemical elements. Alam specifically monitored WASP-62b while swiping in front of the host star three times, making visible light shots, which detect the presence of sodium and potassium in planetary atmosphere.

“I have to admit I wasn’t initially excited about this planet,” Alam says. “But once I started looking at the data, I was excited.”

Although there was no evidence of potassium, the presence of sodium was very clear. The team was able to include the full sodium lines in their data, or their entire fingerprint. Clouds or mist in the atmosphere would hold out the signature of full sodium, Alam explains, and astronomers can usually only make small suggestions as to its presence.

“This is evidence of smoke guns that we see a clear feeling,” she says.

Cloudless planets are rare; astronomers estimate that less than 7 percent of exoplanets have clear environments, according to a recent study. For example, the first and only other known exoplanet with a clear atmosphere was discovered in 2018. Named as WASP-96b, it is considered hot Saturn.

Astronomers believe that studying exoplanets with a cloudless atmosphere will give a better understanding of how they were formed. Their rarity “suggests that something else is going on or that they have created in a different way than most planets,” Alam says. Clear air also makes it easier to study the chemical composition of planets, which helps to identify where a planet is made of.

With the launch of the James Webb Space Telescope later this year, the team hopes to have new opportunities to explore and gain a better understanding of WASP-62b. Improved telescope technologies, such as higher resolution and better precision, should help them study the atmosphere even closer to find more elements, such as silicon.

###

Astrophysics Center Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask – and ultimately answer – the most pressing questions humanity has about the nature of the universe. The Astrophysics Center is headquartered in Cambridge, MA, with research facilities throughout the U.S. and around the world.