Aliens might have sent messages by tweaking variable stars.

galaxyGalaxy NGC 1309, snapped by the Hubble Space Telescope, is packed with Cepheid stars of the type that could form a communication network.NASA, The Hubble Heritage Team and A. Riess (STScI)

Just by gazing at the stars, earthling astronomers might have unwittingly picked up broadcasts from extraterrestrial civilizations. So says a neutrino physicist, adding that it might take researchers just a few months of searching to find evidence of this alien internet.

John Learned at the University of Hawaii in Honolulu and his colleagues think that signals could be sent by manipulating Cepheid variable stars. These rare stars can be seen in other galaxies more than 60 million light years from our own.

Cepheids dim and brighten regularly, in a pattern that depends on their brightness. This lets astronomers measure the distance to the stars, helping to resolve mysteries such as the Universe’s age and how fast it is expanding. As such, any sufficiently advanced civilization would want to monitor such stars, the scientists reasoned.

To send messages using a Cepheid, Learned and his colleagues suggest that extraterrestrials might change the star’s cycle. A Cepheid becomes dimmer as ionized helium builds up in its atmosphere. Eventually, the atmosphere expands and deionizes, restarting the cycle.

Firing a high-energy neutrino beam into a Cepheid could heat its core and brighten the star early — “just as an electric pulse to the heart can make it skip a beat,” Learned says.

The neutrinos could be made by blasting a proton beam at a target — sapphire, carbon or tungsten would work, says Learned. The target produces subatomic particles, mostly pions, which decay to produce neutrinos.

The normal and shortened pulses could be used to encode data, to form what the researchers call a ‘galactic Internet’ in a paper posted to the arXiv preprint server1.

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