Which Stars can see Earth as a Transiting Exoplanet?

TL;DR

This paper identifies stars within 100 parsecs that could observe Earth as a transiting exoplanet, providing a target list for SETI and future missions to search for extraterrestrial life.

Contribution

It compiles a catalog of 1,004 nearby stars capable of detecting Earth's transits, aiding targeted SETI and exoplanet observation efforts.

Findings

Identified 1,004 stars within 100 parsecs that can observe Earth's transit.

77% of these stars are M-type, making them prime targets for SETI.

Provides a target list for future missions like TESS to search for extraterrestrial life.

Abstract

Transit observations have found the majority of exoplanets to date. Spectroscopic observations of transits and eclipses are the most commonly used tool to characterize exoplanet atmospheres and will be used in the search for life. However, an exoplanet's orbit must be aligned with our line of sight to observe a transit. Here we ask, from which stellar vantage points would a distant observer be able to search for life on Earth in the same way? We use the TESS Input Catalog and data from Gaia DR2 to identify the closest stars that could see Earth as a transiting exoplanet: We identify 1,004 Main Sequence stars within 100 parsecs, of which 508 guarantee a minimum 10-hour long observation of Earth's transit. Our star list consists of about 77% M-type, 12% K-type, 6% G-type, 4% F-type stars, and 1% A-type stars close to the ecliptic. SETI searches like the Breakthrough Listen Initiative are already focusing on this part of the sky. Our catalog now provides a target list for this search. As part of the extended mission, NASA's TESS will also search for transiting planets in the ecliptic to find planets that could detect life on our transiting Earth as well.