How old does something need to be officially studied by historians? I'm particularly interested in topics like political history and events that are still controversial today, but occurred within the last 100 years or something. Is there any official limit to the age that something has to be to be examined by historians?
Edit: Thanks for the replies!
I've said it before here, and it's always with restating. The biggest difference between the social sciences is methodology. A bioarchaeologist, a military historian, and a historical archaeologist can both study an American Civil War battlefield. The first might look at injuries on skeletal remains, the second at general's journals, and the third at excavations of a Union fort. The subject matter is exactly the same; they might even contribute to the same article.
Now certain things by their very nature are not studied by a certain field. Historians don't study the 13th century Mississippian metropolises of the central US, just like archaeologists don't write about the US Senate. This is not because of some arbitrary topical or temporal boundary, but because it where their techniques are not particularly helpful. Archaeologists study the material culture of the past; there's not much that can tell us about the Senate that we don't already know. A historian will focus on textual resources; that's not too helpful if a culture didn't use writing. The best social scientists are nominally one profession or another, but are not afraid to try on the hat of another if it may prove helpful.
With specific regards to your question: yes, technically my above reasoning means a historian could study ongoing events. Recording such things can in fact be very helpful for future academics. But at some point you have to ask if it's not something else- journalism, ethnography, sociology... Things from the last five years are technically the past, so a historical approach might reveal something. There's going to 50 different and better ways, though, to understand the events.
Hi, you may be interested in a few responses to a similar question a few days ago
I think it's sort of an unspoken rule that 50 to 100 years should pass before starting to do actual historical research on it. It's really only at that point that all the material starts to "settle" into something discernable in the kind of aggregate hindsight that historians strive for. Imagine trying to write a history book for 2010. It sounds weird to say it, but from a historical perspective we don't really know what happened then, since new things come from 2010 faster than anyone would really be able to compile, record, and analyze.