Underweight, oversized planets formed in outskirts of star systems
NASA, ESA, G. Bacon/STScI
A gassy planet, close to its star, with a puzzlingly small mass.
Not to be confused with a generic breakfast cereal, superpuffs are fluffy planets snuggled up to their suns. A superpuff develops its inflated persona by forming far from its star and then wandering inward, astronomers Eve Lee and Eugene Chiang of the University of California, Berkeley suggest online November 1 at arXiv.org. Starting out in the outskirts of a fledgling planetary system, the researchers say, would mean more cold gas is available to stick to a rocky core.
Superpuffs are quite large for their mass. They typically weigh a few times as much as Earth but stretch up to 10 times as wide. That’s about as large as Jupiter but roughly one one-hundredth of its mass. These puffy worlds are the opposite of the rocky heavyweights known as super-Earths (