SAN FRANCISCO » A prominent astronomer resigned today from the University of California, Berkeley, after an investigation found he sexually harassed female students over many years, two top administrators said.

The university immediately accepted professor Geoffrey Marcy’s resignation, according to a statement from Chancellor Nicholas B. Dirks and Executive Vice Chancellor and Provost Claude Steele. It called Marcy’s conduct "contemptible and inexcusable."

"We also want to express our sympathy to the women who were victimized, and we deeply regret the pain they have suffered," the statement said.

The university has not released details of a six-month investigation into one of the world’s leading experts on planets outside Earth’s solar system, which found he violated the campus’ sexual harassment policies. The inquiry that ended in June stemmed from complaints from former students and involved incidents dating as far back as 2001.

An email to Marcy wasn’t immediately returned. He apologized last week, but the university faced growing pressure to fire him.

"UC Berkeley’s reaction to the finding that Professor Geoff Marcy violated the university’s sexual harassment policies has been the subject of understandable criticism and anger," the administrators said.

After the investigation and the nature of the complaints first were reported by BuzzFeed News, UC Berkeley said Marcy had agreed to clear parameters around his behavior, knowing that he would be subject to automatic suspension or dismissal for any violations.

The school described the agreement Marcy reached with Vice Provost for Faculty Janet Broughton as "the most certain and effective option for preventing any inappropriate future conduct" because it bypassed a lengthy disciplinary process that would have required a hearing before a faculty committee.

Some of Marcy’s colleagues and former students were angry that he had not been sanctioned more severely, including one of the four female students who filed complaints about him with the school last year.

"His job as a professor is to mentor and provide guidance to young people; in that role he’s caused devastating harm," Sarah Ballard, who earned an undergraduate degree in astronomy from Berkeley, told The New York Times.

Ballard, now a post-doctoral fellow at the Massachusetts Institute of Technology, said her former professor talked to her about his sexual experiences as a young man and tried to give her a neck massage one time as she was getting out of his car.

She told The Times she was afraid to confront Marcy or file a complaint because she needed letters of recommendation for graduate school.

Marcy posted a public apology on his website (http://bit.ly/1jtpjrT ) in a letter he sought to have published in the newsletter of the American Astronomical Society’s Committee on the Status of Women in Astronomy. The committee declined his request.

"While I don’t agree with each complaint that has been made, it’s clear my actions made some women uncomfortable and, for that, I sincerely apologize," he told The Associated Press in an email Monday. "I have worked hard to change and will continue to focus my efforts on promoting a supportive and respectful environment both in the astronomy community and more broadly."