Cotton-Candy or Super-puff planets are relatively rare and are found in the system of Kepler-51.

Kepler-51 is an exoplanet system that boasts of three “super-puff” planets orbiting a much younger Sun-like star. This discovery was made by NASA in 2012 through its Kepler Space Telescope. However, the low densities of the planets were determined only in 2014, which was a surprising find for many. The trio exoplanets were named by the scientists as Kepler-51 b, Kepler-51 c, and Kepler-51 d. The Hubble Space Telescope was used to study the densities of the  Kepler-51’s trio and the scientists have reported the Cotton-Candy planets to be located approximately 2,400 light-years from Earth and are identified as a young relative that is 500 million years old.

The atmosphere of the Cotton-Candy planets was not at all transparent when the scientists looked through the Hubble Space Telescope. The atmosphere appeared to be shrouded by a high-altitude layer of something opaque. The group studying the trio further determined using computer simulations and other tools, that the planets of Kepler-51 are mostly helium and hydrogen by mass. These lightweight gases offer puffiness to the Cotton-Candy planets. The planets are also covered by a thick haze of methane. In that sense, the exoplanets have a close resemblance with Titan, the moon of Saturn.

These super-puff worlds have densities less than 0.1 grams per cubic centimeter, while the density of Earth is nearly 55 times greater at approximately 5.5 grams per cubic centimeter. The puffy exoplanets are roughly the size of Jupiter and have a similar density to cotton candy. The researchers of NASA over the years have speculated that the low-density atmosphere will evaporate with time. This will likely result in the formation of Kepler-51 b into a hotter and smaller version of Neptune. The Kepler-51 system offers scientists a unique laboratory for undertaking the testing of theories of early planet evolution. Many details of the Cotton-Candy planets are still not known to the researchers. The upcoming James Webb Space Telescope of NASA, with greater sensitivity to longer wavelengths of infrared light will successfully peer through the layers of cloud. Future observations using this telescope could offer insight as to what these puffy planets are actually composed of.

Only time can tell if these Cotton-Candy planets will acquire resemblance to Neptune in the future.