Most in the astronomy community would align with the statement by Jason Wright, a Penn State astronomy professor that, "you should reserve your alien hypothesis as a last resort." But that's not to say the matter never gets suggested. There is a star, creatively named KIC 8462852, with a dimming behavior scientists can't explain. Naturally, the discussion turned to aliens constructing enormous superstructures that happen to be blocking the stars light from us. The peculiar behavior was discovered by Planet Hunters, an organization that combs through troves of databases to analyze dimming of stars to detect exoplanets (and they're quite successful with this technique). Ultimately, there are many plausible explanations that may apply to the situation .... but aliens is so much more fun.