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Saturday, August 7, 2021

TRACKING WITH CLOSEUPS: Observing Transits of Earth from other Stars

Observing transits, where planets pass in front of the stars they orbit, has become the means by which most exoplanets (planets orbiting other stars) have been discovered. Precision measurements allow detecting the diameter, possible moons, and atmospheric properties of these planets. Future instruments may make it possible to identify signs of life, such as the presence of atmospheric gases (for example, methane and free oxygen) which are produced by living organisms and unstable unless continually replenished by them.

From how may stars, nearby and more remote, might transits of the Earth be observed, and what might alien astronomers learn about Earth? The European Space Agency's Gaia spacecraft, which is assembling a three dimensional map of around a billion stars in the Milky Way, allows estimating this for the first time. The paper, “Past, present and future stars that can see Earth as a transiting exoplanet”, was published in Nature, and is behind a paywall.

Posted at August 7, 2021 12:36