The Allen Telescope Array. Image by SETI astronomer Seth Shostak

Scientists at the SETI (the Search for Extraterrestrial Intelligence) program just announced that they are going to step up their search for alien life. The institute is going to introduce two new methods to comb the skies for signs of extraterrestrial intelligence, increasing their 30 year mission to discover whether or not humanity is alone in the universe.

SETI is a non-profit corporation, that is sponsored by NASA, whose aims are "to explore, understand, and explain the origin, nature, and prevalence of life in the universe." Currently, there are three primary ways that SETI is searching for signs of alien life. The first method involves searching Mars and the distant moons of our solar system for signs of microbes or microorganisms. The second project scans the atmospheres of exoplanets for signs of oxygen or methane. This may seem like an odd way to search for life, but these are gases that, on Earth, are tied to life. The third project involves combing the skies for technologically advanced aliens. Specifically, ones that are sending radio signals (or other such indicators) out into space.

Basic probability says that alien life is out there, and SETI is determined to find it.

One of the new projects is the Panchromatic SETI project, which will look for signals that could be sent out by technologically advanced intelligent lifeforms. For this project, multiple telescopes will scan the radiation that is emanating from 30 nearby stars. SETI is also launching an "interplanetary eavesdropping program." This program will look for messages that are transmitted between two planets in a single system. As Dan Werthimer, director of the Berkeley SETI Research Center, states, "If we are polluting space [and indeed, we are], perhaps other extraterrestrials are leaking signals."

At this point, our older broadcasts (like “I Love Lucy” and “The Ed Sullivan Show”) have passed 10,000 stars (thankfully, reality television hasn't made it too far beyond our own solar system). However, there are an estimated 300 billion stars in the Milky Way alone, so humanity's broadcasts really haven't traveled all that far on the cosmic scale. And if there is life out there, it's unlikely that it will be listening for us on one of the closest stars to Earth. So ultimately, if we want to find intelligent alien civilizations, we're likely going to have to look for it ourselves.

This is where the eavesdropping project comes in. This first SETI project will use data from multi-planet systems that were discovered by NASA's Kepler mission to look for broadcasts that are being transmitted from one planet to another. If there is intelligent life on one planet, it is likely that they will eventually advance technologically and extend to other planets in their solar system. If they do travel to a second planet, signals sent between them should be detectable when the two are lined up  and facing the Earth. This may seem a tad far-fetched, but consider our own exploits on Mars and Venus. Then there are the satellites orbiting Saturn and traveling in the vast darkness of interstellar space. All of these various projects involve a lot of signals being sent about.

However, signals like the ones that are sent to our rovers would be too weak for SETI to detect with its current technology (so would television signals). Distance is ultimately what poses one of the biggest problems when trying to detect extraterrestrials. This is because the required power for a transmitter to be detected increases with the square of the distance. This means that a transmitter that is 150 light-years away would need to be 100 times as powerful as one 15 light-years away. So instead of looking for ET's version of reality TV, scientists will be looking for something that is high-frequency, like the U.S. Air Force's "sky fence," which is a high-frequency radar that is used to track space junk that is in orbit.

According to SETI-Berkeley's Andrew Siemion, chief scientist of the eavesdropping project, the search will also probe deeper into a population that has already been well studied at many wavelengths. "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.

Of course, once we detect the alien signals, we may still need to translate them into something meaningful (we won't be able to determine the purpose of the communication and if it is to a rover or individual), but it will still be a terribly exciting breakthrough.

The second project is the Panchromatic project, which will examine a sample of the 30 stars that lie within 16 light-years from the sun. To date, no confirmed exoplanets have been found around any of the stars that the project will be looking at. Ultimately, SETI is using distance as the criteria because they want to get rid of any potential biases that could result from focusing only on systems that are similar to Earth. The team selected stars for study based only on how far they lie from the sun.

Siemion  rationalizes the choice by asserting, "In the event of a non-detection, these attributes of the sample will allow us to place strong and broadly applicable limits on the presence of technology." Moreover, the close distance of these stars should make it easier to detect signals from any intelligent life.

"Within a couple of parsecs, E.T. wouldn't have to have technology much more advanced than ours in order for us to detect it," Siemion said.



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