If there were alien civilizations, it could observe the Earth from one of the nearest thousand stars, from which it is possible to see our planet transiting against the disk of the Sun. This is indicated by the research published in the Monthly Notices of the Royal Astronomical Society: Letters and coordinated by astronomer Lisa Kaltenegger, of Cornell University.
"If observers were out there looking, from the planets orbiting these stars, they would be able to see the signs of life in the atmosphere of our 'Pale blue dot'", notes Kaltenegger, citing the name of the photo taken. in 1990 by the Voyager 1 probe. As for us, he added, "we are able to see the brightest of these stars in our night sky without the help of binoculars or telescopes."
Most of the alien worlds discovered so far have been found with the technique of transits, ie by observing the passage of these planets against the disk of their stars.
Consequently, the researchers wondered from which stars, using the same technique, a possible alien civilization would be able to search for life on Earth.
They then searched for them in the star catalogs obtained with data from the Tess (Transiting Exoplanet Survey Satellite) satellites, from NASA, and Gaia, from the European Space Agency (ESA).
They have thus identified a total of 1,004, all within the distance of 326 light years.
Of these, 508 guarantee an observation of the Earth against the Sun's disk of at least ten hours.
"If - observed Kaltenegger - we are looking for an intelligent life in the universe capable of finding us, we have just obtained the star map in which we too could try to orient ourselves in the search for a possible alien civilization".
