Polarized Light from
Exoplanets: The Key to Clouds
and Hazes?
Pushkar Kopparla
Vijay Natraj
Yuk Yung
Matthew Wilcoxson
1
Polarization and Exoplanets
UNPOLARIZED
POLARIZED
Stam et al (2004)
UNPOLARIZED
2
Model Setup
From Star
1. Create a model
atmosphere and perform
radiative transfer (with
VLIDORT*)
*Spurr et al (2013)
To Earth
2. Rotate polarization vectors
into equatorial plane and
sum over illuminated disc
3
Model Setup
3. Repeat at various phases and
rotate into Earth’s sky plane
Berdyugina et al (2011)
4. Compare with observations!
4
Polarimetric Observations of HD 189733b
-π
π
0
Observations at 0.36 and 0.44 micron
wavelength
-π
Berdyugina et al (2011)
π
0
5
Model Output: Maximum
Polarization
Rayleigh atmosphere
Geometric albedo 0.5
Model
Observations
Berdyugina et al
(2011)
Conclusions
• Polarized light from exoplanets contains
information about atmospheric structure
and orbital orientation.
• We show that simple Rayleigh scattering
comes close to but cannot fully account
for the observed polarization of HD
189733b.
7
End
Longitude of Ascending Node (omega)
Ω
star
To observer