WASHINGTON - Well-known author and astrophysicist Neil deGrasse Tyson on Sunday denied allegations by 3 women of sexual misconduct spanning several decades.

Tyson, 60, who has built a successful career on television and in his books explaining and popularizing science, had remained largely silent as 3 different women lodged complaints dating as far back as 1984.

But on Sunday, in a lengthy Facebook post, he responded.

"For a variety of reasons," he wrote, "most justified, some unjustified, men accused of sexual impropriety in today's 'me-too' climate are presumed to be guilty by the court of public opinion."

While calling himself a "loving husband... a scientist and educator," he wrote that "accusations can damage a reputation and a marriage. Sometimes irreversibly."

In the first case, a woman alleged that Tyson drugged and raped her when both were graduate students at the University of Texas in 1984. She has said she remembered passing out after he gave her a drink and waking up later, naked, on his bed.

Tyson, in his Facebook post, said he remembered "being intimate only a few times, all at her apartment, but the chemistry wasn't there... There was nothing otherwise odd or unusual about this friendship."

The scientist said he was stunned more than 30 years later to read that he was being accused "of drugging and raping a woman I did not recognize by either photo or name" (she had since married).

Tyson said the allegation stemmed "from an assumption of what happened to her during a night that she cannot remember... as though a false memory had been implanted."

In 2009, he said, a colleague approached him at a conference to ask for a photograph.

She had a tattoo of the solar system that reached up her arm. Tyson admits he likely "search(ed) for Pluto at the top of her shoulder," but said that he was surprised to hear later that she thought he had been "creepy" and had "groped" her.

"That was never my intent and I'm deeply sorry to have made her feel that way," he wrote.

The third allegation dates from this summer. After spending many hours on a project working with a female production assistant, he said, he had invited her to his place for wine and cheese.

Later, "she came into my office to told(sic) me she was creeped out by the wine & cheese evening. She viewed the invite as an attempt to seduce her."

Tyson also admitted having "clumsily" told her more than once that "if I hug you I might just want more." And Tyson said he had offered her a "special" handshake -- which she said seemed overly intimate -- that he said he had learned "from a Native elder on reservation land at the edge of the Grand Canyon."

Fox Broadcasting and National Geographic, which air Tyson's popular show "Cosmos," have said they are investigating his conduct.

The American Museum of Natural History in New York is also looking into the accusations, The New York Times reported. Tyson directs the Hayden Planetarium there.