Every now and again, I screw up.  Oh, it’s extremely rare when I write an article (cough cough), but it happens. Sometimes it’s small enough that I’ll just issue a correction in the text and then forget about it, because hey, that happens. But other times it’s either big enough or an interesting enough mistake that it’s worth following up. Mea culpa is Latin for “my fault.” So, mea culpa . In this case it’s a point I’ve actually made a few times when talking about trying to define what a planet is.  To be clear right off the bat, I have held the position for a long time — and I still do — that the term planet is not definable. It’s a concept, not a hard and fast rule.…