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Friday, September 12, 2008

Aliens might have sent messages by tweaking variable stars

If we received a message from an extraterrestrial civilization, would we necessarily realize it? SETI has long scanned the skies for evidence of alien transmissions, while others have proposed a hunt for physical artifacts sent by our distant neighbors. But neutrino physicists at the University of Hawaii have proposed yet another possibility: that humans have already received an extraterrestrial communication, and that we might find the message in our existing observations of the stars.

Professor John Learned suggested that a civilization could attempt to initiate communication with other advanced civilizations by making unnatural alterations to Cepheids, relatively rare stars that other civilizations are likely to study:

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.

Thus, the Cepheids might provide an intergalactic network of relays, which distant societies could use to broadcast messages to one another. But don't go warming up those neutrinos yet:

[T]he galactic internet would be slow - a Cepheid with a roughly one-day period could transmit about 180 bits per year. Such a transmission would require roughly a millionth of the star's energy, the researchers estimate.

For the time being, it makes more sense to comb through the 100 years' worth of data researchers have collected on the Cephids, searching for irregularities in the pulsing power. Learned estimates:

"Analyzing that data would take a graduate student a couple of months, and just think if it turned out to be correct."

At least the university's indentured academics know how they'll be spending their school year.

Full article here:

'Galactic internet' proposed [Nature]