If the Stay Puft marshmallow man from Ghostbusters were a planet, it would probably be the newly discovered super gas giant, KELT 11b. The highly inflated planet is located some 320 light years away and is 40 percent larger than Jupiter, despite being only a fifth as massive as the largest planet in our solar system.

"We were very surprised by the amazingly low density of this planet," says Lehigh University professor Joshua Pepper who led a team of researchers that discovered the planet. "(It is) about as dense as styrofoam, with an extraordinarily large atmosphere."

The researchers were looking for gas giants around bright stars, but never anticipated finding such huge, low-mass planets. Because the "puffy" planet's star, Kelt 11, is such a bright yellow subgiant sun, Pepper says it allows very precise measurements of the planet's atmosphere.

"(It's) an excellent testbed for measuring the atmospheres of other planets," he explains.

Analyzing the atmospheres of exoplanets to check for possible biosignatures like oxygen and methane is a key next step in searching for other Earth-like planets that might support life beyond our solar system. Next-generation telescopes like the James Webb Space Telescope and the European Extremely Large Telescope in Chile will be key tools in this next phase of the search.

KELT-11b isn't the only puffed-up body in its system. The star, KELT-11 is near the end of its life and expanding into a red giant. Within the next hundred million years it will engulf KELT-11b, which circles it in a tight orbit that takes less than five days. In other words, the cosmic Stay Puft man is about to become a s'more.

The research is published online in The Astronomical Journal.

Source: Lehigh University