Looking for Earth 2.0 in binary systems

A new paper titled "Searching for Habitable Exoplanets with Relative Astrometry (SHERA)" suggests that a NASA Small Explorer mission could use the complex dynamics of binary star systems to find Earth-sized planets in habitable zones. The mission aims to detect periodic shifts in the relative separation of binary stars, which could indicate the presence of exoplanets. The paper outlines a method using a diffractive pupil, a complex phase pattern on a 22-cm space telescope mirror, to achieve sub-microarcsecond precision. The SHERA team has identified seven nearby binary systems within 17 parsecs of Earth, aiming to find up to four small, habitable-zone planets. The mission is expected to help test whether close-in binaries suppress planet formation at certain distances and provide additional context to ground-based radial velocity data.

• The SHERA team has identified seven nearby binary systems within 17 parsecs of Earth.
• The mission is expected to find up to four small, habitable-zone planets across its target stars.
• The mission is designed as a relatively inexpensive NASA Small Explorer (SMEX) mission, potentially helping lower the time required for the Habitable Worlds Observatory (HWO) to characterize planets around those stars.

The SHERA mission is based on the technique of astrometry, which measures the exact position of stars against a background field of other stars. By focusing on bright but closely separated binary pairs, SHERA eliminates background errors and large-scale optical distortions. The mission uses a diffractive pupil to measure optical distortions and thermal expansion of stars, and to correct for stellar activity mimicking planetary signals. The SHERA team's calculations suggest that finding fewer than two planets in the sample would indicate that habitable-zone planet occurrence rates around binaries are significantly lower than expected around single stars. The mission is not yet officially planned as a NASA mission, but it could help reduce the time required for the Habitable Worlds Observatory (HWO) to characterize planets around those stars.

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