Detecting nonsolar planets by spinning infrared interferometer

Abstract

THE only known planets are the nine in our Solar System, so the origin of the Solar System and of stars in general would be clarified if other planetary systems could be discovered. Likewise, speculation about life in the Galaxy would benefit from knowing which stars have planets. Astrometry, radial velocity measurement, and direct photography from orbit might detect planets, but none of these approaches will be easy. Astrometry would require detection of the motion of a stellar image, relative to background stars, by ±0.5 arcms as 12 yr elapse (for a system identical to the Sun plus Jupiter but situated at a distance of 10 pc). Alternatively, a radial velocity change of ±12 m s⁻¹ over the 12 yr would reveal a Jupiter-like planet which would mean detecting a spectral line shift of 2×10⁻⁴ line widths in a line 0.1 nm wide. The instruments required would need stability over a period of years as well as sensitivity. Direct photography from orbit would invoke precision apodisation and would require surface accuracies on optical surfaces of hitherto unattained quality. The new infrared method proposed here also needs to be considered.