Direct Detection of Exoplanets with Optical Polarimetry (1)


Exoplanet Contrast Requirements

Most RV-discovered exoplanets are far too close to their parent stars to be directly imaged
  1. λ / D at 500 nm on a 3-m telescope is similar to λ / D in H band at Keck

  2. Direct imaging of RV-discovered exoplanets in H band requires at least a 30-m telescope

Transiting exoplanets allow direct detection of thermal emission during secondary eclipse, when the exoplanet passes behind its parent star, but this causes two problems:

  1. ≈10% of known exoplanets transit, so the large majority of exoplanets are inacessible to this technique

  2. It is difficult to separate scattered light from the Wien tail of re-radiated thermal emission: close-in exoplanets are so hot that they glow even in the optical

Polarimetry allows direct detection of close-in explanets in scattered light, and the high contrasts necessary (1-10 parts per million) are offset by the differential nature of polarimetry and reduction of systematic effects.

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