Josef Allen Hynek (1910-1986) was an American scientist and Astronomy professor at Ohio State University. In the course of his scientific career, he became Associate Director of the Smithsonian Astrophysical Observatory in 1956, and in 1960 he assumed a position of a chairman of the Astronomy Department at Northwestern University.

Nevertheless, Dr. Hynek is probably best known for his contribution to UFO research, where he is regarded as one of the pioneers of scientific investigation of the phenomenon.

In 1948, Hynek was invited by the US Air Force to act as a technical consultant on Special Project HT-304, or Project Sign (1947-1948), set up to investigate UFO sighting reports which flooded the Air Force at the time, and were causing a considerable concern among the general public.

The Air Force's UFO investigations eventually evolved into Project Blue Book (1952-1969), with J. Allen Hynek as it's chief scientific consultant.

Hynek started off as a skeptic, thinking that his main task will be to educate the public, as well as the Air Force personnel, in matters of astronomy and related atmospheric phenomena. However, he soon realized that not all UFO sightings could be explained as misidentifications of known natural occurrences.

Moreover, a small but persistent percentage of reports of highest quality, filed by competent observers, and containing hard physical data, could not be explained at all. This led him to the conclusion that UFO phenomenon is a real, physical phenomenon, and that it represents "an aspect or domain of the natural world not yet explored by science".[1]

Hynek also noticed that Project Blue Book was not organized as a proper scientific study, but, rather, it appeared to be a public relations project aimed at explaining away as many UFO reports as possible, regardless of scientific plausibility of many of these explanations.

In 1973, four years after the Air Force terminated Project Blue Book, Hynek founded the Center for UFO Studies (CUFOS), a Chicago based civilian UFO research organization.

J. Allen Hynek died in 1986 of a malignant brain tumor at Memorial Hospital in Scottsdale, Arizona.

Allen J. Hynek devised a two-tier, six part UFO classification system based on observed physical properties of an object, as well as proximity to it, and level of interaction between UFO and/ or its occupants, and the environment.

I. Physical Prperties

1 nocturnal lights - sightings of lights in the night sky, that exhibit unusual properties, and cannot be readily explained in terms of natural phenomena, or human-made devices
2 daylight disks - daytime sightings of structured aerial objects of various shapes and sizes, exhibiting exceptional flight capabilities, with no known human technologies and/ or natural phenomena that can account for the observed
3 radar-visual sightings - UFOs tracked on one or more radars, and simultaneously detected visually at the location given by radar readings

II. Proximity and Interaction

4 Close encounter of the first kind (CE-I) - a UFO estimated to have been within cca 500 feet of the witness, causing no interference, and leaving no traces behind upon departure
5 Close encounter of the second kind (CE-II) - a UFO at close proximity, close enough to interfere with car engines, TV and radio signals, affect animal behavior, cause burns and/ or paralysis, and, in case of landing, it leaves markings on the ground
6 Close encounter of the third kind (CE-III) - a sighting of actual UFO occupants, i.e. aliens