Past, Present and Future Stars that can see Earth as a Transiting Exoplanet

TL;DR

This paper identifies stars within 326 light-years that could have observed Earth as a transiting planet since early human civilization and predicts future vantage points, highlighting the dynamic nature of cosmic observation opportunities.

Contribution

It provides a comprehensive catalog of stars with the potential to observe Earth's transit history and future, including known exoplanet hosts and the impact of human radio signals.

Findings

1,715 stars could have seen Earth transit since early human civilization.

319 stars will be able to observe Earth in the next 5,000 years.

Over 75 nearby stars have already been exposed to human-made radio waves.

Abstract

In the search for life in the cosmos, transiting exoplanets are currently our best targets. In the search for life in the cosmos, transiting exoplanets are currently our best targets. With thousands already detected, our search is entering a new era of discovery with upcoming large telescopes that will look for signs of life in the atmospheres of transiting worlds. However, the universe is dynamic, and which stars in the solar neighborhood have a vantage point to see Earth as a transiting planet and can identify its vibrant biosphere since early human civilizations are unknown. Here we show that 1,715 stars within 326 light-years are in the right position to have spotted life on a transiting Earth since early human civilization, with an additional 319 stars entering this special vantage point in the next 5,000 years. Among the stars are 7 known exoplanet hosts that hold the vantage point to see Earth transit, including Ross-128, which saw Earth transit in the past, Teegarden's Star, and Trappist-1, which will start to see Earth transit in 29 and 1,642 years, respectively. We found that human-made radio waves have swept over 75 of the closest stars on our list already.