Two scientists summarize the challenge for finding alien life in the universe.
Look for high amounts of oxygen and mid-infrared energy, the second of which has already produced some candidates.
A recent large survey by the Wide-field Infrared Survey Explorer (WISE) satellite did identify five red spiral galaxies whose combination of high MIR and low near-ultraviolet luminosities are inconsistent with simple expectations from high rates of star formation. A conventional explanation for these observations, such as the presence of large amounts of internal dust, has not been ruled out, however. Such peculiar objects deserve follow-up observations before we explore whether they might represent the signatures of galaxy-dominating species.
The article is very thoughtful, however, and outlines in detail the issues and problems the research faces. We might, in a few decades, have the capability to answer this question, but then, the aliens might be alien enough to still be undetectable. Or they might not exist at all.