The Bloated Hydrogen Envelope and Tidal Distortions of Sub-Neptune Kepler-36c
In the catalog of extrasolar worlds discovered by the Kepler Space Telescope , few systems challenge our understanding of planetary formation as dramatically as Kepler-36 . Located approximately 1,200 light-years from Earth in the constellation Cygnus , this system is home to two planets orbiting in unprecedented proximity. The outer companion, Kepler-36c , is a classic sub-Neptune —a class of planets intermediate in size between Earth and Neptune that has no analogue in our own Solar System. While its inner neighbor, Kepler-36b, is a dense, scorched super-Earth , Kepler-36c is a highly bloated, low-density world wrapped in a massive envelope of primordial hydrogen and helium . First confirmed in 2012 using transit timing variations , Kepler-36c has become a cornerstone target for astrophysicists studying planetary atmospheres, orbital dynamics, and migration theory . The physical contrast between the two tightly packed planets, which orbit their host star at distances differi...