Aliens could have been watching us for 5,000 years and listening to our old radio shows, according to new research.
Scientists have identified at least 29 potentially habitable worlds where ETs could get a good look at us since the time of the pharaohs.
Researchers mapped out Solar Systems in our Milky Way that can support alien life – and are also in a position to observe Earth using telescope techniques similar to our own.
They were a total of 2,034 stars within 326 light years from our planet and some could even be receiving signals from our radios, said the scientists.
Some which had sight of us may now have their view blocked – with 319 to get their first chance to get a glimpse our blue green world using the "transit technique" over the next 5,000 years.
Among them is the Trappist-1 system. It is 45 light years away and home to seven rocky and watery Earth-sized planets – four of which are temperate and habitable.
They will enter the region where they can spot us in 1,642 years and remain there for 2,371 more.
Corresponding author Professor Lisa Kaltenegger, of Cornell University in New York, explained: "From their point of view, we are the aliens.
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"We wanted to know which stars have the right vantage point to see Earth, as it blocks the Sun's light.
"And because stars move in our dynamic cosmos, this vantage point is gained and lost.
"Stars with a vantage point from which they could see Earth transit the Sun could be priority targets for searches for potentially habitable planets."
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The study in Nature is based on data from the European Space Agency's Gaia satellite that has mapped the Milky Way.
A catalogue of stars within around 300 light years enabled a count of those in the right place to have seen Earth since the early pharaohs.
And 75 are even close enough to hear the sounds of our radio stations that began broadcasting into space about a century ago.
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Co-author Dr Jackie Faherty, of the American Museum of Natural History in New York, said: "Gaia has provided us with a precise map of the Milky Way galaxy.
"It has allowed us to look backward and forward in time – and to see where stars had been located and where they are going.
"Our solar neighbourhood is a dynamic place where stars enter and exit that perfect vantage point to see Earth transit the Sun at a rapid pace."
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By watching distant exoplanets transit – or cross – their own sun, astronomers can interpret the backlit atmospheres.
If they harbour intelligent life, the chemical signatures can be identified.
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