Scientists from Canada, Germany, Japan and the United States found that WASP-107b, detected in 2017 in about 212 light years from Earth in the Virgo constellation, is as big as Jupiter but 10 times lighter, which makes it one of the least dense exoplanets discovered so far. Astrophysicists call such celestial bodies "super-puff" or "cotton-candy" planets.
"We reveal that WASP-107b's mass is only 1.8 Neptune masses (M b = 30.5 ± 1.7 M ⊕). The resulting extraordinarily low density suggests that WASP-107b has a H/He envelope mass fraction of >85% unless it is substantially inflated. The corresponding core mass of <4.6 M ⊕ at 3σ is significantly lower than what is traditionally assumed to be necessary to trigger massive gas envelope accretion," the article’s abstract read.
The researchers note that WASP-107b "presents a challenge to planet formation theories" and "will be a keystone planet to understand the physics of gas envelope accretion."