(Proposal ID) S12A-015

(PI) de Kok, Remco

(Proposal Title)
Characterising the planets around HR 8799 using near-infrared polarimetry

(Abstract)
We aim to detect the first polarisation signatures of thermal radiation of an 
exoplanet, using polarimetric direct imaging of the HR 8799 planetary system 
in H and K-band, where simulations show that the degree of polarisation can be 
up to several percent. Polarimetry can give access to planetary 
characteristics that are otherwise unobtainable: a single detection of 
polarised thermal emission immediately confirms the presence of scattering 
clouds in the planet's atmosphere and the degree of polarisation constrains 
atmospheric inhomogeneities and the planet's rotation rate. The polarisation 
angle can directly yield the components of the planetary spin axis normal to 
the line of sight, giving unprecedented insights into the debated formation 
mechanism of the HR 8799 system.