If there are aliens in nearby star systems, they may have already spotted Earth


A view of the Earth and the sun thousands of miles above our planet. The stars that move in and out of a position where they can see Earth as a planet in transit around our sun are illuminated.

OpenSpace / American Museum of Natural History

Scientists scan the cosmos for possible signals from extraterrestrial civilizations for decades, but for over a century, humans have also sent signals from Earth that could be picked up by aliens beyond our planet. In other words, if they are looking for the right place for us.

New research has determined exactly which star systems have been – or will be – able to spot Earth and mark it as a potential hotbed for intelligent life that is worth investigating further (or perhaps avoiding altogether). .

“Any civilization with our level of technology could have seen us already,” Lisa Kaltenegger, professor of astronomy at Cornell, told me by email.

Kaltenegger and astrophysicist Jackie Faherty of the American Museum of Natural History used data from the European Space Agency Gaia Space Observatory identify 2,034 nearby systems with promising perches for spotting certain human extraterrestrials.

“We wanted to know which stars have the right vantage point to see Earth because it blocks sunlight,” she said. “And because the stars move through our dynamic cosmos, that point of view is won and lost. I was wondering how long this front row seat to find Earth through the hard star’s declining brightness. did not know. ”

Kaltenegger and Faherty exploited the latest and extensive Gaia Star Catalog, which contains both star positions and movement, to find answers.

“So you can project their movement into the future and trace it back to the past,” says Kaltenegger.

They discovered that 1,715 of the star systems were in the correct position to have spotted the Earth passing by or passing through the sun since human civilization began about 5,000 years ago. The other 319 systems will move into a position with line of sight to Earth over the next 5,000 years.

In an article published online Wednesday in the journal Nature, scientists further zoomed in on 75 systems that were within this ideal range of human spotting, called the Earth’s transit zone, since commercial radio stations began sending out reports. scattering signals in space that travel outward in the cosmos at the speed of light.

So if anyone or something in these systems is operating a radio telescope like one of ours, they may already be enjoying some old-fashioned radio drama from Earth right now.

“Our analysis shows that even the closest stars typically spend more than 1,000 years at a vantage point from which they can see the transit of Earth,” the article read. “This provides a long time frame for nominal civilizations to identify Earth as an interesting planet.”

Scientists have also identified seven of the 2,034 star systems known to host exoplanets. These included Ross 128, a red dwarf star just 11 light-years away from an Earth-sized planet. The world could have seen the Earth a little over 3,000 years ago, but it left the observation zone about 900 years ago.

“Has anyone concluded that there was intelligent life on Earth 900 years ago?” asks Kaltenegger.

the Trappist System-1 is only 45 light years from us and is home to seven Earth-sized planets, four of which are in the habitable zone, but they probably aren’t spying on us. At least not yet – their path will bring them into the Earth’s transit zone where they could observe us, but not for 1642 years.

Three star systems host exoplanets that should be able to see Earth now and for hundreds of years to come, but they are all over 200 light years away, meaning our commercial radio signals don’t have them. not yet achieved.

On the scale of the entire Milky Way galaxy, it is still practically next door. Researchers hope their work will help inform science using exciting new technology that is fast approaching as the next one James Webb Telescope or Breakthrough Starshot’s plan to send a tiny spacecraft to check on the Alpha Centauri system and its known exoplanet just 4.2 light years away.

“You could imagine that worlds beyond Earth that have already detected us, are making the same plans for our planet and our solar system,” Faherty said. “This catalog is an intriguing thought experiment that one of our neighbors might be able to find us for.”

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