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Past, present and future stars that can see Earth as a transiting exoplanet

Abstract

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. Previous work has explored the zone from which Earth would be visible while transiting the Sun1,2,3,4. However, these studies considered only the current position of stars, and did not include their changing vantage point over time. Here we report that 1,715 stars within 100 parsecs from the Sun are in the right position to have spotted life on a transiting Earth since early human civilization (about 5,000 years ago), with an additional 319 stars entering this special vantage point in the next 5,000 years. Among these stars are seven known exoplanet hosts, including Ross-128, which saw Earth transit the Sun in the past, and Teegarden’s Star and Trappist-1, which will start to see it in 29 and 1,642 years, respectively. We found that human-made radio waves have already swept over 75 of the closest stars on our list.

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Fig. 1: Stars that can see Earth transit since early human civilization.

Data availability

All data are available in the Supplementary Information and at https://github.com/jfaherty17/ETZ.

Code availability

Code used in the analysis is available at https://github.com/jfaherty17/ETZ.

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Acknowledgements

L.K. acknowledges support from the Carl Sagan Institute at Cornell and the Breakthrough Initiative. J.K.F. acknowledges support from the Heising Simons Foundation and the Research Corporation for Science Advancement (award 2019-1488). This work has made use of data from the European Space Agency (ESA) mission Gaia, processed by the Gaia Data Processing and Analysis Consortium DPAC20 (https://www.cosmos.esa.int/gaia, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research also used NASA’s Astrophysics Data System and the VizieR and SIMBAD databases operated at CDS, Strasbourg, France.

Author information

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Authors

Contributions

L.K. conceived the idea of the study and J.K.F identified the ETZ stars. L.K. and J.K.F composed the manuscript, undertook the analysis and discussed the content of this manuscript.

Corresponding author

Correspondence to L. Kaltenegger.

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The authors declare no competing interests.

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Peer review information Nature thanks the anonymous reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

A guide to Supplementary Tables 1 and 2.

Supplementary Table 1

Stars that can see Earth transit in the +/-5000-year period. This Table lists all characteristics for stars that can see Earth transit in the +/-5000-year period, sorted by distance from the Sun. The authors cross-matched their full sample against literature estimates of mass, effective temperature, radii, bolometric luminosity, metallicity, and log g for Gaia sources. Respective catalogue references for the parameter are noted in Table 1 and Table 2.

Supplementary Table 2

Exoplanet host stars that can see Earth transit in the +/-5000-year period. This table lists the characteristics of the seven known stars that can see Earth transit in the +/-5000-year period, that are known exoplanet host stars, sorted by distance from the Sun.

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Kaltenegger, L., Faherty, J.K. Past, present and future stars that can see Earth as a transiting exoplanet. Nature 594, 505–507 (2021). https://doi.org/10.1038/s41586-021-03596-y

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