Vol. 559
In section 10. Planets and planetary systems

Warm ice giant GJ 3470b. I. A flat transmission spectrum indicates a hazy, low-methane, and/or metal-rich atmosphere

The blue sky of GJ3470b: the atmosphere of a low-mass planet unveiled by ground-based photometry

The planet GJ 3470b is slightly less massive and slightly larger than Uranus and transits its star, an M dwarf approximately half the mass of the Sun, every 3.3 days. The system is only about 30 parsecs away and has therefore been the object of the attention of telescopes around the world. Two papers in this issue bring new information to help constrain the atmospheric properties of this planet. Crossfield et al. present new observations of the transits of the planets at 2.09 to 2.36 microns using the Keck/MOSFIRE spectrograph. Their results point to a flat transmission spectrum indicative of a hazy, low-methane or metal-rich atmosphere. Nascimbeni et al. also observe the transits, but in the ultraviolet (0.36 microns) and in the optical infrared (0.96 microns) using the LBC camera at the Large Binocular Telescope. They detect much more absorption in the UV (i.e. a larger planet), indicative of the presence of hazes in the atmosphere. Dynamical models including clouds and radiative transfer should be conducted to constrain the properties of this intriguing atmosphere.