(CNN) According to Carrie Fisher there was a reason she and Harrison Ford had such chemistry in "Star Wars."

Almost 40 years later the actress says she and Ford had an affair on the set of the now iconic 1977 film.

"It was so intense," Fisher told People magazine . "It was Han and Leia during the week, and Carrie and Harrison during the weekend."

Fisher, 60, has a new book coming out based on her diaries from that time.

"The Princess Diarist" is billed as "Carrie Fisher's intimate, hilarious and revealing recollection of what happened behind the scenes on one of the most famous film sets of all time, the first 'Star Wars' movie."

Fisher was 19 when she landed the breakthrough role of Princess Leia for the 1976 filming. Ford, then 33, was married to Mary Marquardt, with whom he had two children.

The couple divorced in 1979. Harrison later married "E.T.: The Extra Terrestrial" screenwriter Melissa Mathison in 1983, and they divorced in 2004.

He's been married to actress Calista Flockhart since 2010.

Fisher writes that she and Ford spent their first night together after a birthday party for director George Lucas.

"I looked over at Harrison. A hero's face -- a few strands of hair fell over his noble, slightly furrowed brow," she wrote. "How could you ask such a shining specimen of a man to be satisfied with the likes of me?"

"I was so inexperienced, but I trusted something about him," she added. "He was kind."

Naturally Fisher's revelations have provided lots of fodder for social media.

I can't say I'm shocked that Carrie Fisher had an affair with Harrison Ford. What bothers me is that she didn't care he was married. — Alicia Stockton (@alliedoll42) November 16, 2016

Carrie Fisher "reveals" that she had an affair with Harrison Ford while filming the original #StarWars.



Because no one guessed. No one. — Giacomo G Casanova (@CasanovasTool) November 16, 2016

In March, Fisher appeared on the British talk series "The Jonathan Ross Show" and denied she and Ford had been romantic.

She said she thought he looked like a movie star. "It wasn't like you get a crush on that person."

However, Fisher said at the time that her recently found journals had more details.

"I haven't looked all the way through it, but I must say it seemed to be trending in that direction," she said. "But it didn't happen."

Pressed by Ross, she said she was still poring through the diaries for details.

"It might happen, it might now happen," Fisher said.

Ford and Fisher reprised their roles last year in " Star Wars: The Force Awakens ."

CNN has reached out to Ford for comment.