Here is the name of the professor who came up with the theory and what he has to say on things:

Antonio Paris, a professor of astronomy at St Petersburg College in Florida, thinks the signal might have come from one or more passing comets. He points the finger at two suspects, called 266P/Christensen and P/2008 Y2 (Gibbs). “I came across the idea when I was in my car driving and wondered if a planetary body, moving fast enough, could be the source,” he says.

If the comets were passing in front of the Big Ear in 1977, they would have generated an apparently short-lived signal, as the telescope (now dismantled) had a fixed field of view.

What do you think is this a reasonable explanation?  Feel free to comment.

And here is kind of a comical pic of what alien emojis might look like

thanks to newscientist.com for the great info