This lopsided galaxy is a mess. But why?

In astronomy, like with most fields of science, there are mysteries we run across we can’t explain. In movies and TV show this usually means some extremely weird phenomenon that’s about to fall from the sky or break out of a beaker and wreak havoc, and the scientist in the story has no idea why.

In real life though the mystery is usually a little less life-threatening and more of a “Huh. I wonder what’s going on here?” kind of a thing. And the problem isn’t that we don’t have an explanation, it...