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 \mu m spectroscopy of the middle planet , HR 8799 c , which has an estimated mass of \sim 10 M _ { Jup } , temperature of \sim 1100 K and projected separation of 38 AU .
The spectrum shows some differences in the continuum from existing theoretical models , particularly longwards of 4 \mu m , implying that detailed cloud structure or non-equilibrium conditions may play an important role in the physics of young exoplanetary atmospheres .