TOKYO (Reuters) - Japan's next prime minister might be nicknamed "the alien," but it's his wife who claims to have had a close encounter with another world.

"While my body was asleep, I think my soul rode on a triangular-shaped UFO and went to Venus," Miyuki Hatoyama, the wife of premier-in-waiting Yukio Hatoyama, wrote in a book published last year.

"It was a very beautiful place and it was really green."

Yukio Hatoyama is due to be voted in as premier on September 16 following his party's crushing election victory over the long-ruling Liberal Democratic Party on Sunday.

Miyuki, 66, described the extraterrestrial experience, which she said took place some 20 years ago, in a book entitled "Very Strange Things I've Encountered."

When she awoke, Japan's next first lady wrote, she told her now ex-husband that she had just been to Venus. He advised her that it was probably just a dream.

"My current husband has a different way of thinking," she wrote. "He would surely say 'Oh, that's great'."

Yukio Hatoyama, 62, the rich grandson of a former prime minister, was once nicknamed "the alien" for his prominent eyes.

Miyuki, also known for her culinary skills, spent six years acting in the Takarazuka Revue, an all-female musical theater group. She met the U.S.-educated Yukio while living in America.

(Reporting by Colin Parott; Editing by Linda Sieg)