Analysis of planet effect of reference star on searching for Earth-like planets

Abstract

It is a challenging task to find exoplanets because of the huge contrast between star and planets in mass and in brightness. It is more challenging to determine the masses of exoplanets because it requires extremely high astrometric accuracy. In particular detection of Earth-like planets needs sub-microarcsecond (µas) precision which is possible only by narrow-angle astrometry via the SIM PlanetQuest mission. The narrow-angle observation mode of SIM PlanetQuest requires several distant reference stars, which are close enough in the sky around the target, typically within one degree. This paper provides statistical estimates of available reference stars for all candidate stars in searching for Earth-like planets.It is inevitable that some of reference stars will have binary components and planets. This paper describes the analysis techniques and various error estimates for binary jitters and planet effects of reference stars. Because of the limited number and duration of observations of SIM PlanetQuest, the Monte Carlo simulations indicate that certain long period planets around reference stars may not be detected. Earth-like planets around target stars, however, can be detected unambiguously. Finally, we demonstrate the current best estimates of instrument error, photon noise, reference stars planet disturbance, stellar jitters, etc., and conclude that the orbits of Earth-like planets with sub-µas astrometric signatures can be determined accurately by SIM PlanetQuest for nearby candidate stars.

Overview of the SIM PlanetQuest Light mission concept

“…This accuracy is achieved by multiple visits to the target stars. SIM-Lite will achieve 1.4 µas differential error between Tier 1 target position and a set of Reference stars [12] per 12-chop visit. Most Tier-1 target will require more than 12 chops per visits, the average being around 60 chops per visits to lower the instrument accuracy down to the required level for detection of 1-Earth mass planet.…”