Searching for habitable exoplanets with relative astrometry Part I. The case for searching for planets in binary star systems

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Abstract
Discovering Earth-like planets orbiting Sun-like stars was identified as a priority science goal of the Astronomy 2020 Decadal Survey. It is confounded by many factors, one of which is the high multiplicity of Sun-like stars in the local neighborhood—half of nearby Sun-like stars are in binary or higher-order stellar systems, which are less amenable to the detection of small planets with almost all of the currently productive exoplanet detection techniques. We describe the SHERA (Searc+hing for Habitable Exoplanets with Relative Astrometry) NASA Small Explorer mission concept. SHERA utilizes diffractive-pupil technology on a small, simple optical space telescope to achieve microarcsecond precision relative astrometry on 14 Sun-like stars in seven nearby multistar systems, combining the pupil and stellar binarity to provide a precise reference in the image plane. With this precision, SHERA would enable the following: (i) a search for rocky planets in the habitable zones of the closest Sun-like stars; (ii) an investigation of the impact of binary star formation on small, widely separated planets; and (iii) the performance of crucial precursor observations on a number of high-priority targets of NASA’s future missions to characterize Earth-like planets, such as the Habitable Worlds Observatory. When combined with radial velocity measurements, SHERA relative astrometry will also enable exploration of the three-dimensional orbital structure of planets in binary systems.
Funding Information
  • National Aeronautics and Space Administration (80NM0018D0004)