The WISE Telescope
In 1964, Russian scientist Nikolai Kardashev suggested that in the long history of the universe, which began billions of years before the origin of our Sun and Earth, really advanced civilizations might have developed. Such civilizations might learn to control the total power of their stars -- and, ultimately, the total power of their galaxies.
Now, Jason Wright and Roger Griffith, a pair of scientists at Penn State University, have actually searched for this last kind of super-civilization. If such advanced beings have actually colonized and exploited the billions of stars within a galaxy, these civilizations could produce tremendous amounts of waste heat.
Just like your car and your computer produce waste heat while they are operating, so the thought is that large-scale civilizations will generate an unnatural amount of heat, beyond the heat that all objects give off.
A recent satellite called the Widefield Infrared Survey Explorer (WISE) has been collecting information on sources of heat energy around the sky. Wright and Griffith have looked at the output of 100,000 galaxies, to see if anyone of them might betray signs that the heat they produce is not natural, but comes from a super-civilization.
Although they did not find any obvious and definitive evidence, they did note some galaxies whose infrared energy was unusual in some ways. These are worth investigating further.
Of course no one really knows whether intelligent creatures can ever evolve to a level of technology where they take over an entire galaxy. So finding one by this method is a long shot. (But I asked Geoff Marcy, the world's leading planet hunter, and he pointed out that just about all our searches for intelligence in the universe so far have been "long shots" -- no one can be sure today what method will pay off. So Marcy feels we should explore as many different methods as possible.)
I also asked Jill Tarter, the U.S. leader of the search for extra-terrestrial intelligence using radio waves, and she also was excited about our adding more techniques to our SETI arsenal. She told me she was adding the unusual galaxies from the WISE survey to the list of places where they would point radio telescopes, just in case there were any intelligent radio signals to be found.
Indeed, the SETI institute organized a Google hangout about this survey, and included Jill Tarter and Freeman Dyson, who first suggested ways that an advanced civilization might betray itself with infrared waves. You can hang out and see what they said at: https://plus.google.com/events/cs8lq28m1ebd2bnukspml93njc8