A new 'puffy' planet has been discovered in the Kepler-47 system

Kepler-47 is a 3.5-billion-year-old star system about 3,340 light years away from Earth. It's one of nine systems that we know of that are "binary star systems," which means it has not one star at its heart, but two. And it's the only one we know that has two planets orbiting around it: Kepler-47b and Kepler-47c.

Well, make that three.

Scientists have officially confirmed the existence of a third planet orbiting the binary stars of Kepler-47, and have appropriately dubbed it Kepler-47d, Space reported. The newly discovered planet is about seven times bigger than Earth, making it the largest planet in its system, roughly double the size of Kepler-47b and c.

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The discovery, announced in The Astronomical Journal on Tuesday, is big news for the team that discovered it. Kepler-47d's orbit lies in between Kepler-47b's and Kepler-47c's, even though scientists theorized that any additional planets would be found further away from the stars.

The Kepler-47 trio is helping scientists learn about so-called "puffy" planets, which are gas planets with a large size but a very low density. Even the puffiest planet in our solar system, Saturn, is much denser than any of the Kepler planets. The information we can learn about them will help us understand more of the "loosely packed, low-density planets" in our solar system, said Jonathan Fortney, an astronomer at the University of California, Santa Cruz. Read more at Space.