There seems to be some confusion as to whether a question can be asked if the questioner knows the answer. I have asked some questions where I knew the answer and have often received answers I was not aware of. In addition as I have mentioned in the past new questions are needed to keep the site fresh and interesting. What are the thoughts of others on meta?
See also: meta.judaism.stackexchange.com/questions/139/…– Isaac Moses ModDec 22, 2011 at 22:36
Stack Exchange is fairly adamant that asking and answering your own question is perfectly fine. As a result, every SE FAQ, including ours, says so in the first section.
I would add, though, that people who do this should be very careful to avoid a pitfall that's naturally associated with it: skimping on question quality. People who ask questions they don't know an answer to are naturally motivated to put as much detail and motivation as possible into the question, to help others give answers that are as helpful as possible. People who already know an answer, by contrast, are much more likely to post just enough of a question to serve as a set-up, in their own heads, to the answer they know.
Consequently, I think it's important to make sure to write all questions from the point of view of someone who doesn't know an answer, and accordingly, include as much information as possible to help answerers. In particular, if your Q&A is motivated by the fact that you were curious about something, found an answer, and want to share it with the world, you should remember what you were thinking in the curious phase when writing the question.
UPDATE: Reflecting on this question it seems to me that it's worth drawing a distinction based on where the question is coming from. Is it plausible to say that the question is based on curiosity about something, where knowing or seeing one thing makes you wonder about something else? In that case, you've probably got a question that will fit our format well. On the other hand, if the question mainly comes from knowing the answer and wanting to let people know about it, it may be difficult to express it in a useful, non-leading way.
Funny. The question that sparked your update (which is closed as not a real question) is really interesting, at least once his comments are taken into consideration. On the other hand, SimchasTorah asks a lot of leading questions and posts the answer immediately - sometimes so quickly that it suggests that he not only knew the answer beforehand but had even written it beforehand! Those are the ones that bother me the most, especially when (as is usually the case) he selects his own answer as the best. I would have left open the constellation question and closed every SimchasTorah leading one.– Seth JMay 23, 2012 at 17:03
2@SethJ, My point is that I don't care what the asker/answerer actually knew, when; I care about whether the question is written in a way that would attract people who have a similar point of curiosity. In the Virgo case, it's hard to imagine anyone being curious about what the Torah origins of the constellation's name are if they didn't already know about those origins. If we were a bulletin board for Torah ideas rather than a Q&A community, that would be fine, but we're not. See also meta.judaism.stackexchange.com/a/1086/2 .– Isaac Moses ModMay 23, 2012 at 17:12