LOS ANGELES - When Leonard Nimoy was approached about acting in a new TV series called "Star Trek," he was, like any good Vulcan contemplating a risky mission in a chaotic universe, dispassionate.

"I really didn't give it a lot of thought," he later recalled. "The chance of this becoming anything meaningful was slim."

By the time "Star Trek" finished its three-year run in 1969, Nimoy was a cultural touchstone _ a living representative of the scientific method, a voice of pure reason in a time of social turmoil, the unflappable and impeccably logical Mr. Spock

He was, as the Los Angeles Times described him in 2009, "the most iconic alien since Superman" - a quantum leap for a character actor who had appeared in plenty of shows but never worked a single job longer than two weeks.

Nimoy, who became so identified with his TV and film role that he titled his two memoirs, somewhat illogically, "I Am Not Spock" (1975) and "I Am Spock" (1995), died Friday at his home in the Bel-Air neighborhood of Los Angeles. He was 83.

The cause was end-stage chronic obstructive pulmonary disease, said his son, Adam.

Nimoy revealed last year that he had the disease, a condition he attributed to the smoking he gave up 30 years earlier.

While he was best known for his portrayal of the green-tinted Spock, Nimoy more recently made his mark with art photography, focusing on plus-sized nude women in a volume called "The Full Body Project" and on nude women juxtaposed with Old Testament tales and quotes from Jewish thinkers in "Shekhina."

He also directed films, wrote poetry and acted on the stage.

As Spock, he was the pointy-eared, half-Vulcan, 23rd-century science officer whose vaulted eyebrows seemed to express perpetual surprise at the utterly illogical ways of the humans who served with him on the starship Enterprise.

Spock could barely wrap his mind around feelings. He was the son of a human mother and a father from Vulcan - a planet whose inhabitants had chosen pure reason as the only way they could survive. When he thwarted deep-space evil-doers, it was with logic simple enough for a Vulcan but dizzying for everyone else, including his commanding officer, Capt. James T. Kirk, played by William Shatner.

While worlds apart from the racial strife and war protests of the 1960s, "Star Trek" explored such issues by setting up parallel situations in space, "the final frontier."

"Spock was a character whose time had come," Nimoy later wrote. "He represented a practical, reasoning voice in a period of dissension and chaos."

He also turned Nimoy into an unlikely sex symbol.

When he spoke at Ohio's Bowling Green State University in the 1970s, a young woman asked: "Are you aware that you are the source of erotic dream material for thousands and thousands of ladies around the world?"

"May all your dreams come true," he responded.

Trekkies everywhere greeted each other with Nimoy's "Vulcan salute" _ a gesture he adapted from one he had seen at an Orthodox synagogue when he was a boy.

"I was awestruck," Nimoy recalled in a 2004 Times interview.

At the altar, five or six men chanted prayers with their arms raised. They held their hands with fingers parted between the ring and middle fingers and thumbs stuck out _ a representation, Nimoy said, of the Hebrew letter "shin," the start of "Shaddai," a term for God.

LSD guru Timothy Leary once flashed Nimoy the Vulcan salute. So did cabdrivers who sped by on the street, and interviewers who momentarily suspended their journalistic detachment. At a 2007 fundraiser in Los Angeles, presidential candidate Barack Obama spied Nimoy across a room, smiled, and held up his hand in the familiar gesture.

Four years later, President Obama told ABC's Barbara Walters that his critics wrongly believed he was "Spock-like," or too analytical.

For much of his career, Nimoy had to deal with the same sort of perception problem.

While his 1975 autobiography was "I Am Not Spock," he later called the title a mistake because it was so easily misconstrued. In the book, he said he couldn't think of a TV character he would sooner have played.

At the same time, he was disquieted by mountains of fan mail addressed not to Leonard Nimoy, but to "Mr. Spock, Hollywood, Calif."

The melding of actor and character was sometimes uncomfortable. On a tour of California Institute of Technology, Nimoy was asked his thoughts about complex projects by students who must have believed he had a Spock-like insight.

"I would nod very quietly, and very sagely I would say, 'You're on the right track,'" he told The New York Times in 2009.

Nimoy appeared in the original "Star Trek" TV series, which ran on NBC from 1966 to 1969. He received three successive Emmy nominations.

He also was Spock in feature films, including: "Star Trek: The Motion Picture" (1979); "Star Trek II: The Wrath of Khan" (1982); "Star Trek III: The Search for Spock" (1984); "Star Trek IV: The Voyage Home" (1986): "Star Trek V: The Final Frontier" (1989); and "Star Trek VI: The Undiscovered Country" (1991).

He retired from "Star Trek" pictures until 2009, when he became Spock Prime, a Mr. Spock who inhabited an alternate universe in J.J. Abrams' "Star Trek." He did a cameo performance as the same character in "Star Trek Into Darkness" (2013).

Rumors of Spock's impending on-screen demise in "Star Trek II" prompted death threats to director Nicholas Meyer.

"I received a helpful letter that ran: 'If Spock dies, you die,'" Meyer wrote in "The View from the Bridge: Memories of Star Trek and a Life in Hollywood."

The scene was filmed anyway _ so affectingly, according to Meyer, that the crew wept openly "as the dying Spock held up his splayed hand and enjoined Kirk to 'live long and prosper.'"

Thanks to an ancient Vulcan ceremony