Super-puff worlds: These Jupiter-sized planets are light as cotton candy

Astronomers once believed that most solar systems would be much like our own, with small rocky planets near their sun, accompanied by gas giants orbiting the star at greater distances. Beginning in 1992, researchers began to find worlds orbiting alien stars, and soon found solar systems came in a wide variety of formations. Today, astronomers know of more than 4,000 worlds orbiting other stars. Of these, 15 have exceedingly low densities, lower than that of cotton candy. Three of these planets — dubbed super-puff worlds — are found in the Kepler 51 star system, 2,600 light years from Earth. Larger…

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