The unpublished KELT-11b is 40% larger than Jupiter but less than a quarter of its mass. Their find opens the door to study new types of atmospheres.

A planet made of cork, this time small.

Cork (also known in Spain as porexpan, polystyrene or any term that sounds similar and is derived from expanded polystyrene foam) is the typical material with which children build their solar systems at school. It is easy to shape, it is light to hang and above all, it is resistant to falls.

Therefore, it is not entirely surprising that researchers at Lehigh University (Pennsylvania, United States) have discovered that the planet KELT-11b, which is 320 light years from Earth has a density of about 30 kilograms per cubic meter, just like cork.

Illustration of KELT-11b orbiting close to its star.

Illustration of KELT-11b orbiting close to its star.
Walter Robinson

“It is very inflated, so while represents only a fifth of the mass of Jupiter, occupies almost 40 percent more, making it as dense as Styrofoam and with an extraordinarily large atmosphere, “says Joshua Pepper, an astronomer at the American university who led the study that appears this week in The Astronomical Journal.

The planet is an almost unprecedented example of a gaseous planet that, rotating very close to its star, has swelled and multiplied in volume. The star it revolves around, KELT-11, has started to turn into a red giant that will end up engulfing this planet within a hundred million years.

Pepper, acting natural.

Pepper, acting natural.
Stephanie Veto

However, before that happens, KELT-11b can be of great use to Earthlings. The brightness of the accompanying star will allow scientists accurately measure the composition of this curious atmosphere and develop tools to discriminate between different types of gases, crucial for next-generation telescopes that will appear over the next decade, such as the James Webb Space Telescope. “It’s an excellent test bed for measuring the atmospheres of other planets,” adds Pepper.

The scientists do not yet know what mechanisms they produce the atmospheric swelling of planets like this one, which is the third least dense for its size ever discovered. “The project is specifically designed to discover a few scientifically valuable planets orbiting very bright stars, and KELT-11b is an excellent example of that,” concludes the astrophysicist.