The littlest Messier object: M40
I love those posters of the Messier objects—especially the ones in color where you can see the lovely nebulas and galaxies in all their glory. [cue soaring classical music[
And then there's M40. [screech of needle skipping off phonograph]
If you're contemplating the Messier marathon this weekend, it pays to know what you're looking for. In this case, an unremarkable double star. It's not hard to find, but M40 does seem like a plastic mug among Ming vases.
The SEDS database points out that this is an optical (line-of-sight) double, not a binary system. In 1863 the angular separation was 49.2" and in 1991 it had increased to 52.8". So assuming they keep moving apart at this rate (3.6" every 128 years), it will only take another 1,880 years to double their current angular separation, which will hardly count as a double star at all.
So I guess the moral of the story is, check out M40 now while it still looks like something.