The detectability of extrasolar planet surroundings

I. Reflected-light photometry of unresolved rings

¹ Observatoire de Haute-Provence, CNRS, 04870 Saint-Michel-l'Observatoire, France
² Observatoire de Paris-Meudon, 92195 Meudon Cedex, France e-mail: Jean.Schneider@obspm.fr

Corresponding author: L. Arnold, arnold@obs-hp.fr

Received: 20 November 2003
Accepted: 9 March 2004

Abstract

It is expected that the next generation of high-contrast imaging instruments will deliver the first unresolved image of an extrasolar planet. The emitted thermal infrared light from the planet should show no phase effect assuming the planet is in thermal equilibrium. But the reflected visible light will vary with phase angle. Here we study the photometric variation of the reflected light with orbital phase of a ringed extrasolar planet. We show that a ring around an extrasolar planet, both obviously unresolved, can be detected by its specific photometric signature. A simple quantitative model is discussed, taking into account the basic optical and geometrical properties of the ringed planet.