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Researchers discover "super fluffy" planet with cotton candy-like density

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Researchers discovered a huge planet 1,200 light years from Earth with a density comparable to that of cotton candy, scientists said Monday. 

WASP-193b is an exoplanet, which means it's located outside of our solar system, according to a study published Tuesday in the journal Nature Astronomy. It's 50% larger than Jupiter — the largest planet in our solar system — but seven times less massive because of its extraordinarily low density. 

"The planet is so light that it's difficult to think of an analogous, solid-state material," Julien de Wit, MIT professor and study co-author, said in a news release. "The reason why it's close to cotton candy is because both are pretty much air. The planet is basically super fluffy."

The extremely low density makes WASP-193b an anomaly among the more than 5,000 exoplanets scientists have discovered to date, researchers said. The only planet scientists have found that is less dense thank WASP-193b is Kepler-51d, a Neptune-like planet that was discovered a decade ago. 

Researchers believe that WASP-193b, which orbits a Sun-like star every 6.25 days, is mostly made of hydrogen and helium. They said the gasses likely form a hugely inflated atmosphere, but said it's unknown how a planet is able to inflate so much. 

"We don't know where to put this planet in all the formation theories we have right now, because it's an outlier of all of them," Francisco Pozuelos, study author and astronomer at the Instituto de Astrofisica de Andalucia, said in a statement. "We cannot explain how this planet was formed."

The planet is a "cosmic mystery," Khalid Barkaoui, lead study author, said. Barkaoui hopes to solve that mystery by measuring atmospheric properties using the James Webb Space Telescope, he said.

Scientists use the term "Super-Puffs" to refer to the unique class of exoplanets with cotton candy-like density. NASA says nothing like them exists in our solar system.

Researchers in 2019 announced the discovery of WASP-107b, another puffy exoplanet. WASP-107b is about the same size as Jupiter, but only about one-tenth the mass. 

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