Improving Earth-like planets' detection with an ELT: the differential radial velocity experiment

¹ LESIA, Observatoire de Paris-Meudon, 5 place J. Janssen, 92195 Meudon, France e-mail: riaud.pierre@obspm.fr
² Université de Liège, 17 Allée du 6 Août, 4000 Sart Tilman, Belgium e-mail: riaud@astro.ulg.ac.be
³ LUTH, Observatoire de Paris-Meudon, 5 place J. Janssen, 92195 Meudon, France e-mail: jean.schneider@obspm.fr

Received: 11 January 2007
Accepted: 17 February 2007

Abstract

Context.Direct detection of Earth-like planets around a nearby star is extremely difficult for ground-based telescopes equipped with the eXtreme Adaptative Optics system.

Aims.We propose to combine high-precision radial velocity with an ELT to detect extrasolar planets with a feasible coronagraph.

Methods.In this context, we investigated the detectability of Earth-like extrasolar planets with an ELT of 42 m equipped with the spectro-coronagraphic instrument in an eXtrem Adaptive Optics system. Those stellar residuals left uncorrected by the XAO wavefront correction (Strehl ratio >85%) system need to be calibrated. We propose calibrating them by the radial velocity measurement of the planet in a multiple spectrum correlation process.

Results.This method allows detection of Terrestrial planets with an ELT but requires a long exposure time (200 h)

Conclusions.The technique overcomes the main coronagraphic limitation due to the pinned and the low variable speckles and opens a way to detect directly exoplanets with large ground-based telescopes equipped with an efficient XAO system.