The Hynek Scale UFO Sightings Encounter Classification System

UFO Sightings protocol
Also called the Close Encounter classification system, the Hynek scale is named after American astronomer and ufologist J. Allen Hynek. The classification was first introduced in his 1972 book  The UFO Experience: A Scientific Inquiry (available here in PDF)

Nocturnal Lights

Lights in the night sky.

Daylight Discs

UFOs seen in the daytime, generally having discoidal or oval shapes.


UFO Sightings reports that seem to have radar confirmation. Though seeming to offer harder evidence of physical reality, the vagaries of radar propagation often make the ascription ambiguous.

Close Encounters of the First kind

Visual UFO sightings of an unidentified flying object seemingly less than 500 feet away that show an appreciable angular extension and considerable detail.

Close Encounters of the Second kind

A UFO Sightings event in which a physical effect is alleged. This can be interference in the functioning of a vehicle or electronic device; animals reacting; a physiological effect such as paralysis or heat and discomfort in the witness; or some physical trace like impressions in the ground, scorched or otherwise affected vegetation, or a chemical trace.

Close Encounters of the Third kind

UFO Sightings encounters in which an animated creature is present. These include humanoids, robots, and humans who seem to be occupants or pilots of a UFO.

Close Encounters of the Fourth kind

A UFO Sightings event in which a human is abducted by a UFO or its occupants. This type was not included in Hynek’s original close encounters scale.

Hynek’s erstwhile associate Jacques Vallee argued in the Journal of Scientific Exploration that a CE4 should be described as “cases when witnesses experienced a transformation of their sense of reality”, so as to also include non-abduction cases where absurd, hallucinatory or dreamlike events are associated with UFO Sightings encounters. The film The Fourth Kind makes reference to this ranking.

Close Encounters of the Fifth kind

A UFO event that involves direct communication between aliens and humans. This type of close encounter was named by Steven M. Greer’s CSETI group and is described as bilateral contact experiences through conscious, voluntary and proactive human-initiated cooperative communication with extraterrestrial intelligence.

Close Encounters of the Sixth kind

Death of a human or animal associated with a UFO sighting, although some might consider this as a more severe example of a second-kind encounter.

Close Encounters of the Seventh kind

The creation of a human/alien hybrid, either by sexual reproduction or by artificial scientific methods.

Close Encounters of the Eighth kind

The eighth class is related to a sequence of different kinds of encounter for an individual.

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