![]() This fall, researchers noticed evidence of a strange radio emission while looking through archival data from 2019. Ref: Past, Present And Future Stars That Can See Earth As A Transiting Exoplanet : /abs/2107.Scientists detected a mysterious radio signal from a nearby galaxy, which begs the question-could it be aliens?Īs part of the Search for Extraterrestrial Intelligence (SETI) program, astronomers working on the Breakthrough Listen project scan for radio signals that could come from some non-human intelligent life in the cosmos. It could even prompt searches for radio signals that may already be reaching us from these places. If astronomers find similar conditions elsewhere, that will pique their interest. Life first emerged here some 4 billion years ago, ultimately giving our atmosphere its rich oxygen content and its other biomarkers, such as methane. To similarly equipped alien eyes, Earth will have long looked an interesting target. The next generation of space telescopes should allow astronomers to study these worlds in more detail, to determine their atmospheric make up and perhaps see continents and oceans. Of course, the possibility of life on these worlds is entirely unknown. “Restricting the selection to the distance radio waves from Earth have traveled- about 100 light-years - leads to an estimated 29 potentially habitable worlds that could have seen Earth transit and also detect radio waves from our planet,” say Kaltenegger and Faherty. So there should be at least 508 rocky planets in this population with a good view of earth. Rocky ExoplanetsĮxoplanet statistics suggest that at least 25 per cent of these stars will have rocky exoplanets. “1,715 stars within 326 light-years are in the right position to have spotted life on a transiting Earth since early human civilization, with an additional 319 stars entering this special vantage point in the next 5,000 years,” they say. So Kaltenegger and Faherty also pick out at the star systems set to receive our signals in the next 200 years or so and will also be able to see us. Our signals continue to radiate away from us. Then there is Teegarden’s Star, with at least two Earth-mass exoplanets and the Trappist-1 star system with seven Earth-sized planets, of which four are in the habitable zone. The researchers say, for example, that the Ross128 star system is the 13th closest to the Sun and the second closest with a transiting Earth-size exoplanet. ![]() These systems are generally well studied. Astronomers have already observed exoplanets orbiting four of them. ![]() Kaltenegger and Faherty say 75 stars systems that can see us, or soon will, sit within this 100 light year sphere. Since Gaia measures how these stars are moving relative to one another, the researchers can work out for how long we have been visible to them and for how much longer. Kaltenegger and Faherty’s project is a good example. The resulting map is giving astronomers an entirely new way to study our galactic environment. The data comes from the European Space Agency’s Gaia spacecraft that was launched in 2013 and is mapping the position and motion of some 1 billion astronomical objects. ![]() 3D Star MapĪll this is made possible by the Gaia Catalogue, a new 3D map of our galaxy showing the distance and motion of more than 100 million stars. These astronomers have calculated the size of the sphere that our radio signals have covered since they left Earth, counted the stars that sit inside it and worked out which of them should also be able to see Earth transiting the Sun. Now we get an answer thanks to the work of Lisa Kaltenegger at Cornell University in Ithaca and Jackie Faherty at the American Museum of Natural History in New York City. ![]()
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