An international team of astronomers estimate that there should be approximately ten currently undiscovered worlds which are favorably located to detect the Earth and are capable of sustaining life as we know it. To date however, no habitable planets have been discovered from which a civilization could detect the Earth with our current level of technology.
A group of scientists from Queen's University Belfast and the Max Planck Institute for Solar System Research in Germany have turned exoplanet-hunting on its head, in a study that instead looks at how an alien observer might be able to detect Earth using our own methods. They find that at least nine exoplanets are ideally placed to observe transits of Earth, in a new work published in the journal Monthly Notices of the Royal Astronomical Society. Illustration of an exoplanet. (Ricardo Ramirez MIT).
Image below shows where transits of our solar system planets can be observed. Each line represents where one of the planets could be seen to transit, with the blue line representing Earth; an observer located here could detect us. (2MASS / A. Mellinger / R. Wells)
Thanks to facilities and missions such as SuperWASP and ...