Since humans made their first FM radio and television transmissions, signals from Earth have been spilling out into space, announcing the presence of intelligent life to any group that might be searching for it. According to Werthimer, signals from the 1950s television show “I Love Lucy” have reached thousands of stars, while the nearest suns have already enjoyed the “The Simpsons.”

If Earth has unintentionally leaked signs of its presence, other alien civilizations may have done the same thing. SETI’s new Panchromatic project will utilize a variety of telescopes covering a range of frequencies to scour the nearest stars.
“We’re going to throw everything we’ve got at it,” Werthimer added.

The panchromatic project will examine a sample of the 30 stars that lie within 5 parsecs (16 light-years) from the sun. The list includes 13 single stars, seven binary systems and one triple system. Most of the stars are smaller than the sun, but the project will also examine two white dwarfs and one moderately evolved F star. No confirmed exoplanets have been found around any of the stars.

By setting distance as the criteria, the SETI team hopes to alleviate any bias that might otherwise result from focusing on systems similar to that of Earth. The team selected stars for study based only on how far they lie from the sun.

The second SETI project will make use of the observations of multi-planet systems gathered by NASA’s Kepler mission as it attempts to eavesdrop on signals broadcast from one planet to another.

The Kepler telescope detects planets as they pass in front of their stars, causing a dip in the stars’ brightness. If two planets lie in the same orbital plane, pointed toward Earth, they will occasionally line up. If an intelligent species originated on one planet in a system, then went on to explore or inhabit a second planet, signals sent from one planet to the other should be detectable when the two are lined up facing the Earth.

So far, the team has observed about 75 of these events in multi-planet systems using the Green Bank Telescope. The range of radio frequencies include those used on Earth to communicate with craft sent to other planets.

“Our detection algorithms are sensitive to communications like those used by NASA’s Deep Space Network to communicate with spacecraft, so if E.T. broadcasts something similar at sufficient power, we could hear it,” Siemion said.

Detecting such signals doesn’t necessarily mean researchers will be able to translate them. Scientists may not be able to determine if the communication is to an outpost or a rover. However, that won’t make the discovery any less exciting.

Though a signal between planets should be detectable, Siemion said that it is more likely that a broad signal would be intercepted. Although terrestrial television broadcasts in large beams, these would be too weak to detect under the current experiments. Instead, scientists would be looking for something like the U.S. Air Force’s “sky fence,” a high-frequency radar used in an attempt to track space junk in orbit.

Distance poses one of the biggest problems in eavesdropping on extraterrestrials. The required power for a transmitter to be detected increases with the square of the distance. A transmitter 150 light-years away would need to be 100 times as powerful as one 15 light-years away, if everything else remains the same.  
Most of the Kepler planets and planetary candidates lie at significant distances from Earth, making it difficult for scientists to detect weaker signals like those emitted by spacecraft communication. However, if alien civilizations used something akin to Arecibo, Siemion said, scientists would stand a far better chance of detecting it.