There was a recent paper produced on Omuamua, an interstellar object that recently was seen transiting through our solar system. Avi Loeb speculates that it might be an alien probe. The dude is not an obvious crackpot - he's the head of Harvard's astronomy program. Pretty much everyone is pissing on him for suggesting it.
Link: https://blogs.scientificamerican.com/observations/how-to-approach-the-problem-of-oumuamua/
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