Readings from the Hubble Space Telescope have shed light on a bizarre class of alien planets that have the density of cotton candy.
- The “super-puff” planets were detected by NASA’s Kepler space telescope in 2012, orbiting Kepler 51, a sunlike star that’s 2,600 light-years from Earth along our Milky Way galaxy’s Orion spiral arm. A couple of years later, astronomers determined that the planets — known as Kepler-51 b, c and d — have extremely low densities. Hubble’s recent observations have confirmed those findings.
- Each of the three planets has a size in the range of Saturn or Jupiter, but is roughly 100 times lighter in terms of mass. The Hubble team tried to analyze the atmospheres of 51 b and 51 d, but couldn’t get a good reading of any chemical signatures. “We were clouded out!’ Jessica Libby-Roberts, a planetary scientist at the University of Colorado at Boulder, said today in a NASA feature about the research.
- The planets’ composition may still be a mystery, but that hasn’t stopped Libby-Roberts and her colleagues from theorizing about their origins. They surmise that the planets formed farther out in the Kepler 51 system, and migrated inward. If that hypothesis is correct, the planets’ cotton candy atmospheres should melt away into space over the next few billion years.
Libby-Roberts is the lead author of a paper about the Hubble findings, “The Featureless Transmission Spectra of Two Super-Puff Planets,” due for publication in The Astrophysical Journal.
