Astronomers say they've found a helium exoplanet inflated like a balloon.

Astronomers have found a helium-rich exoplanet that's inflated like a balloon. HAT-P-11b is located in the Cygnus constellation, is roughly the size of Neptune and resides about 124 light years from here.  The University of Exeter describes the exoplanet's helium as "an extended cloud that is escaping from the planet, just as a helium balloon might escape from a person's hand." Vincent Bourrier, one of the authors of the study, further explains: "Helium is blown away from the day side of the planet to its night side at over 10,000 km an hour. Because it is such a light gas, it escapes easily from the attraction of the planet and forms an extended cloud all around it."  That inflation is said to be related to the body's proximity to its star, about twenty times closer than our planet is to the Sun.