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Are you there, aliens? It’s us, Earth. Astronomers have sent a radio message to a neighbouring star system – one of the closest known to contain a potentially habitable planet – and it’s nearby enough that we could receive a reply in less than 25 years.

“I think that’s an unlikely outcome, but it would be a welcome outcome,” said , president of Messaging Extraterrestrial Intelligence (METI) International. METI is an offshoot of the more familiar SETI – the Search for Extra-Terrestrial Intelligence.

The target star is GJ 273, also known as Luyten’s star, a red dwarf in the northern constellation of Canis Minor, just 12 light years away. In March of this year it was discovered to have two planets. One of them, known as GJ 273b, orbits within the star’s “habitable zone” and could potentially harbor liquid water, and perhaps life.

Telling time

This missive to the stars was sent on the anniversary of the “Arecibo message,” a radio transmission beamed toward a distant star cluster in 1974 from the Arecibo radio telescope in Puerto Rico. The Arecibo message contained information on the planets of our solar system, the structure of DNA, a cartoon-like picture of what a human being looks like, and other basic information about the earth and its inhabitants.

This new message – beamed from an antenna in Norway over roughly eight hours over a three-day period in October – is simpler and may be more readily understood, Vakoch says.

It begins with information about counting, arithmetic, geometry, and trigonometry, and includes a description of the radio waves that carry the message, as well as a tutorial on clocks and timekeeping, to see if any potential inhabitants of GJ 273b have an understanding of time similar to our own.

Inviting our own doom?

The idea of intentionally sending messages into space has always been controversial, even within the SETI community. One issue is that it’s far from clear who should speak for humankind. Another concern is the potential danger of reaching out to extraterrestrials.

Physicist Stephen Hawking and others have warned against the possible repercussions of encountering an alien civilization – noting that such a civilization will almost certainly be far older and far more technologically advanced than our own.

“Ninety-eight percent of astronomers and SETI researchers, including myself, think that METI is potentially dangerous, and not a good idea,” says , a SETI researcher at the University of California at Berkeley. “It’s like shouting in a forest before you know if there are tigers, lions, and bears or other dangerous animals there.”

Read more: We still haven’t heard from aliens – here’s why we might never