An artist’s impression of the Kepler 51 system. Image: NASA/ESA/STScI
Imagine a world as large as Jupiter with the density of cotton candy. A young star 2,400 light years from Earth features three such puff-ball worlds, relative rarities in the exoplanet catalogue that raise new questions about how planets form and evolve.
First described in 2014, the three planet’s making up the Kepler 51 system already were known to be among the lowest density worlds yet found. An international team of researchers decided to take a closer look with the Hubble Space Telescope, developing new estimates of mass and density.
They found all three planets have a density of less than 0.1 grams per cubic centimetre – roughly identical to that of cotton candy.
“We knew they were low density,” said Libby-Roberts, a graduate student at the University of Colorado at Boulder. “But when you picture a Jupiter-sized ball of cotton candy, that’s really low density.”
Expecting to spectroscopically detect the presence of water molecules and other atmospheric components, the researchers found the atmospheres were, in fact, opaque, as if blanketed by a Titan-like high-altitude haze.
Using computer modelling and other tools, the team theorises the atmospheres are ...