Deep dive into the mysterious atmosphere of the warm Neptune Gliese 436 b

Star system: Gliese 436 | Distance from the Sun: 31.9 light years

Astronomers have conducted the most detailed study to date of GJ 436 b, a famous 'warm Neptune' exoplanet located 33 light-years away. Despite its similarities to our own Neptune, this world orbits its red dwarf star so closely that its year lasts only 2.6 days. 

New high-resolution observations found no traces of expected gases like water vapor or methane, leading scientists to conclude that the planet is either shrouded in extremely high-altitude clouds or possesses an incredibly dense, metal-rich atmosphere—potentially 900 times more enriched than our Sun. These findings help explain why this planet remains one of the most elusive targets for atmospheric characterization, even with today's most powerful telescopes.

Scientific study

Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES+ observations (external link)