It’s September 1947, and the U.S. Air Force has a problem. A rash of reports about mysterious objects in the skies has the public on edge and the military baffled. The Air Force needs to figure out what’s going on—and fast. It launches an investigation it calls Project Sign.

By early 1948 the team realizes it needs some outside expertise to sift through the reports it’s receiving—specifically an astronomer who can determine which cases are easily explained by astronomical phenomena, such as planets, stars or meteors.

For J. Allen Hynek, then the 37-year-old director at Ohio State University’s McMillin Observatory, it would be a classic case of being in the right place at the right time—or, as he may have occasionally lamented, the wrong place at the wrong one.

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The adventure begins

Dr. J. Allen Hynek with Police Chief Robert R. Taylor of Dexter, Michigan going over a county map spotting where the flying objects were seen, 1966. Bettmann Archive/Getty Images

Hynek had worked for the government during the war, developing new defense technologies like the first radio-controlled fuse, so he already had a high security clearance and was a natural go-to.

“One day I had a visit from several men from the technical center at Wright-Patterson Air Force base, which was only 60 miles away in Dayton,” Hynek later wrote. “With some obvious embarrassment, the men eventually brought up the subject of ‘flying saucers’ and asked me if I would care to serve as consultant to the Air Force on the matter… The job didn't seem as though it would take too much time, so I agreed.”

Little did Hynek realize that he was about to begin a lifelong odyssey that would make him one of the most famous and, at times, controversial scientists of the 20 century. Nor could he have guessed how much his own thinking about UFOs would change over that period as he persisted in bringing rigorous scientific inquiry to the subject.

“I had scarcely heard of UFOs in 1948 and, like every other scientist I knew, assumed that they were nonsense,” he recalled.

Project Sign ran for a year, during which the team reviewed 237 cases. In Hynek’s final report, he noted that about 32 percent of incidents could be attributed to astronomical phenomena, while another 35 percent had other explanations, such as balloons, rockets, flares or birds. Of the remaining 33 percent, 13 percent didn’t offer enough evidence to yield an explanation. That left 20 percent that provided investigators with some evidence but still couldn’t be explained.

The Air Force was loath to use the term “unidentified flying object,” so the mysterious 20 percent were simply classified as “unidentified.”

In February 1949, Project Sign was succeeded by Project Grudge. While Sign offered at least a pretense of scientific objectivity, Grudge seems to have been dismissive from the start, just as its angry-sounding name suggests. Hynek, who played no role in Project Grudge, said it “took as its premise that UFOs simply could not be.” Perhaps not surprisingly, its report, issued at the end of 1949, concluded that the phenomena posed no danger to the United States, having resulted from mass hysteria, deliberate hoaxes, mental illness or conventional objects that the witnesses had misinterpreted as otherworldly. It also suggested the subject wasn’t worth further study.

Project Blue Book is born

That might’ve been the end of it. But UFO incidents continued, including some puzzling reports from the Air Force’s own radar operators. The national media began treating the phenomenon more seriously; LIFE magazine did a 1952 cover story, and even the widely respected TV journalist Edward R. Murrow devoted a program to the topic, including an interview with Kenneth Arnold, a pilot whose 1947 sighting of mysterious objects over Mount Rainier in Washington state popularized the term “flying saucer.” The Air Force had little choice but to revive Project Grudge, which soon morphed into the more benignly named Project Blue Book.

Hynek joined Project Blue Book in 1952 and would remain with it until its demise in 1969. For him, it was a side gig as he continued to teach and to pursue other, non-UFO research, at Ohio State. In 1960 he moved to Northwestern University in Evanston, Illinois, to chair its astronomy department.

As before, Hynek’s role was to review the reports of UFO sightings and determine whether there was a logical astronomical explanation. Typically that involved a lot of unglamorous paperwork; but now and then, for an especially puzzling case, he had a chance to get out into the field.

There he discovered something he might never have learned from simply reading the files: how normal the people who reported seeing UFOs tended to be. “The witnesses I interviewed could have been lying, could have been insane or could have been hallucinating collectively—but I do not think so,” he recalled in his 1977 book, The Hynek UFO Report.

“Their standing in the community, their lack of motive for perpetration of a hoax, their own puzzlement at the turn of events they believe they witnessed, and often their great reluctance to speak of the experience—all lend a subjective reality to their UFO experience.”

For the rest of his life Hynek would deplore the ridicule that people who reported a UFO sighting often had to endure—which, in turn, caused untold numbers of others to never come forward. It wasn’t just unfair to the individuals involved, but meant a loss of data that might be useful to researchers.

“Given the controversial nature of the subject, it’s understandable that both scientists and witnesses are reluctant to come forward,” says Jacques Vallee, co-author with Dr. Hynek of The Edge of Reality: A Progress Report on Unidentified Flying Objects. “Because their life is going to change. There are cases where their house is broken into. People throw stones at their kids. There are family crises—divorce and so on… You become the person who has seen something that other people have not seen. And there is a lot of suspicion attached to that.”

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Eyes on the skies—and the Soviets

Dr. J. Allen Hynek (right) pointing out a spot on a globe to fellow scientists while discussing the path of Sputnik 1, the first artificial satellite launched into low Earth orbit by the Soviet Union, in Cambridge, Massachusetts, October 1957. ( Dmitri Kessel/The LIFE Picture Collection/Getty Images

In the late 1950s, the Air Force faced a more urgent problem than hypothetical UFOs. On October 4, 1957, the U.S.S.R. surprised the world by launching Sputnik, the first artificial space satellite—and a serious blow to Americans’ sense of technological superiority.

At that point, Hynek had taken leave from Ohio State to work on a satellite-tracking system at Harvard, notes Mark O’Connell in his 2017 biography, The Close Encounters Man. Suddenly Hynek was on TV and holding frequent press conferences to assure Americans that their scientists were closely monitoring the situation. On October 21, 1957, he appeared on the cover of LIFE with his boss, the Harvard astronomer Fred Whipple, and their colleague Don Lautman. It was his first taste of the national celebrity, but wouldn’t be the last.

With Sputnik circling the earth every 98 minutes, often visible to the naked eye, many Americans began looking skyward, and UFO sightings continued unabated.

From Dr. Hynek to Mr. UFO

Dr. J. Allen Hynek, telling newsmen at a press conference that the photograph he is holding, widely circulated in the news media as a UFO spotted in Michigan, is a time exposure of the crescent moon and the planet Venus. Bettmann Archive/Getty Images

By the 1960s, Hynek had emerged as the nation’s—perhaps the world’s—top expert on UFOs, quoted widely in his capacity as scientific consultant to Project Blue Book. But behind the scenes, he chafed at what he perceived as the project’s mandate to debunk UFO sightings. He was also critical of its procedures, judging the Blue Book staff “grossly inadequate,” its communication with outside scientists “appalling” and its statistical methods “nothing less than a travesty.”

The feeling, apparently, was mutual. In an unpublished manuscript unearthed by biographer O'Connell, Air Force Major Hector Quintanilla, who headed the project from 1963 to 1969, writes that he considered Hynek a “liability.”

Why did he stick around? Hynek offered a number of explanations. “But most importantly,” he wrote, “Blue Book had the store of data (as poor as they were), and my association with it gave me access to those data.”

If Hynek often angered UFO debunkers, like Quintanilla, he didn’t always please the believers, either.

In 1966, for example, he went to Michigan to investigate multiple reports of strange lights in the sky. When he offered the theory that it might have been an optical illusion involving swamp gas, he found himself widely derided in the press and “swamp gas” became a punchline for newspaper cartoonists. More seriously, two Michigan Congressmen, including Gerald R. Ford (who later became president), took umbrage at the apparent insult to their state’s citizenry and called for a Congressional hearing.

Testifying at the hearing, Hynek saw an opportunity to plead the case he’d been making to the Air Force for years, but with little success. “Specifically, it is my opinion that the body of data accumulated since 1948…deserves close scrutiny by a civilian panel of physical and social scientists…for the express purpose of determining whether a major problem really exists.”

Hynek would soon get his wish, or so it seemed. Now facing greater scrutiny in Congress, the Air Force established a civilian committee of scientists to investigate UFOs, chaired by a University of Colorado physicist, Dr. Edward U. Condon. Hynek, who would not be on the committee, was hopeful at first. But he lost faith two years later when the committee issued what came to be known as the Condon Report.

He called the report “rambling” and “poorly organized” and Condon’s introductory summary “singularly slanted.” Though the report cited numerous UFO incidents its researchers couldn’t explain, it concluded that “further extensive study of UFOs probably cannot be justified.” It was exactly what Hynek wouldn’t have wanted.

The following year, 1969, Project Blue Book shut down for good.

After Blue Book, a new chapter

UFO expert Dr. J. Allen Hynek holds a pipe and one of his magazine editorials while serving as technical advisor for the film, 'Close Encounters of The Third Kind.' Columbia Tristar/Getty Images

The end of Blue Book proved a turning point for Hynek. As O'Connell writes, he “found himself suddenly liberated from the frustrations, compromises and bullying of the U.S. Air Force. He was a free man.”

Meanwhile, sightings continued around the world—UFOs, Hynek later quipped, “apparently did not read the Condon Report”—and he went on with his research.

In 1972, he published his first book, The UFO Experience. Among its contributions to the field, it introduced Hynek’s classifications of UFO incidents he called Close Encounters.

Close Encounters of the First Kind meant UFOs seen at a close enough range to make out some details. In a Close Encounter of the Second Kind, the UFO had a physical effect, such as scorching trees, frightening animals or causing car motors to suddenly conk out. In Close Encounters of the Third Kind, witnesses reported seeing occupants in or near a UFO.

Though less remembered now, Hynek also provided three classifications for more distant encounters. Those involved UFOs seen at night (“nocturnal lights”) during the day (“daylight discs”) or on radar screens (“radar/visual”).

The most dramatic of Hynek’s classifications, Close Encounters of the Third Kind, would, of course, become the title of a Steven Spielberg movie released in 1977. O'Connell reports that Hynek was paid $1,000 for the use of the title, another $1,000 for the rights to use stories from the book and $1,500 for three days of technical consulting—hardly a windfall by Hollywood standards. He also had a brief cameo in the film, playing an awestruck scientist when the alien craft comes into close view.

In 1978, Hynek retired from teaching, but he continued to collect and evaluate UFO reports under the auspices of the Center for UFO Studies, which he had founded in 1973. The organization continues to this day.

Hynek died in 1986 at age 75, the result of a brain tumor. He hadn’t solved the riddle of UFOs but, perhaps more than anyone else, he had made trying to solve that riddle a legitimate scientific pursuit.

“The main thing I got from my father in this whole thing was how important it was to keep an open mind,” says his son, Joel Hynek, who as a young ham-radio operator used to record many of his father’s witness interviews. “He kept saying, ‘You know, we don’t know still everything there is to know about the universe… There could be aspects of physics that we haven’t come upon yet.’”

WATCH: Full episodes of Project Blue Book online now.