Spatially resolved spectroscopy of the exoplanet HR 8799 c

TL;DR

This study presents spatially resolved mid-infrared spectroscopy of exoplanet HR 8799 c, revealing spectral differences from models that suggest complex cloud structures or non-equilibrium atmospheric conditions.

Contribution

First spatially resolved spectroscopy of HR 8799 c in the 3.88-4.10 micron range, providing new insights into its atmospheric properties.

Findings

Spectral continuum differs from existing models, especially beyond 4 microns.

Indications of complex cloud structures or non-equilibrium chemistry in the atmosphere.

Highlights the importance of detailed atmospheric modeling for young exoplanets.

Abstract

HR 8799 is a multi-planet system detected in direct imaging, with three companions known so far. Here, we present spatially resolved VLT/NACO 3.88--4.10 micron spectroscopy of the middle planet, HR 8799 c, which has an estimated mass of ~10 Mjup, temperature of ~1100 K and projected separation of 38 AU. The spectrum shows some differences in the continuum from existing theoretical models, particularly longwards of 4 microns, implying that detailed cloud structure or non-equilibrium conditions may play an important role in the physics of young exoplanetary atmospheres.