This "puffy planet" outside our solar system may hold opportunities for testing atmospheres that will be useful when assessing future planets for signs of life, researchers said.
"It is highly inflated, so that while it is only a fifth as massive as Jupiter, it is nearly 40 per cent larger, making it about as dense as styrofoam, with an extraordinarily large atmosphere," said Joshua Pepper, assistant professor at Lehigh University in the US.
Styrofoam is a kind of expanded polystyrene used especially for making food containers.
"The planet's host star is extremely bright, allowing precise measurement of the planet's atmosphere properties and making it an excellent test-bed for measuring the atmospheres of other planets," Pepper said.
The planet, called KELT-11b, is an extreme version of a gas planet, like Jupiter or Saturn, but is orbiting very close to its host star in an orbit that lasts less than five days.
The star, KELT-11, has started using up its nuclear fuel and is evolving into a red giant, so the planet will be engulfed by its star and not survive the next hundred million years.
"The KELT project is specifically designed to discover a few scientifically valuable planets orbiting very bright stars, and KELT-11b is a prime example of that," Pepper said.
The star, KELT-11, is the brightest in the southern hemisphere known to host a transiting planet by more than a magnitude and the sixth brightest transit host discovered to date.
Though researchers are debating the cause of KELT-11b's inflation, further study of the planet could provide additional information about the mechanism that causes inflated planets, Pepper said.
The planet's large atmosphere also provides good opportunities for developing techniques needed to identify chemicals to assess habitability or products of life in the atmospheres of other planets.
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