Truly Trivial: What events comprise a close encounter of the fifth kind?

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Hot on the heels of last week's Nerd Word -- Majestic 12 -- we return to the surprisingly timely topic of alien abduction. Most of the current upturn in alien interest is due to the new Milla Jovovich movie The Fourth Kind, which ostensibly profiles alien abductees using real (for Blair Witch Project values of real) interview footage. The film's title refers to the fourth type of so-called close encounter, wherein humans are abducted by the occupants of UFOs. Setting aside the plausibility of actual UFO abductions, have you ever wondered who it was that conjured up this enumerated spectrum of close encounters?

Look no further than one J. Allen Hynek, an astronomer and ufologist who had the distinction of both working for Project Bluebook -- the U.S. Air Force investigation into UFO phenomena -- and for publishing a moderately famous book on the subject, The UFO Experience: A Scientific Inquiry. Hynek is the founder of the Center for UFO Studies and, as much as such a thing is possible, is considered a reliable authority on unidentified flying object investigations. In the aformentioned UFO Experience, Hynek laid out three kinds of close encounters to categorize the various UFO reports that he had analyzed (and, most often, debunked) during his tenure as adviser to the Air Force and as a civilian investigator:

1. Close encounter of the first kind, wherein a UFO is merely observed
2. Close encounter of the second kind, wherein physical evidence of a UFO is recovered
3. Close encounter of the third kind, wherein the occupants of a UFO are observed
   

Despite what Jovovich's PR folks might have you believe, there was no fourth kind of close encounter when Hynek published the scale in 1972. Nor did he explicitly add a fourth kind to the scale before his death in 1986. This was added later by other ufologists, with some significant contributions by Jacques Vallée, Hynek's frequent collaborator and perhaps the only other well known "respectable" UFO researcher. (Vallée was the real-life inspiration for the lead research scientist character, Lacombe, in Steven Spielberg's Close Encounter's of the Third Kind.)

For his part, Vallée did not explicitly endorse the alien abduction defintion of fourth kind of close encounter, but merely described them as "cases when witnesses experienced a transformation of their sense of reality." Vallée was equally circumspect as to the definition of a close encounter of the fifth kind, the most involved and potentially definitive UFO interaction of the revised close encounter scale.

So, what events comprise a close encounter of the fifth kind?