What star will blow up next?

In the live chat tonight, I was asked when Betelgeuse will explode. The answer is, we don't know. :-) But that made me think about other stars that will blow, almost certainly before Betelgeuse does. I recorded my answer. The stars I mention are Sher 25 and Eta Carinae. For the record, I said that I thought Sher 25 was 6000 light years away; it's actually 6000 parsecs, or 20,000 light years away. I had the number right, but the unit wrong. :-) You can read all you want about Supernova 1987A on my Bitesize Pages, too.