Olivia Newton-John, the Grammy-winning superstar who reigned on pop, country, adult contemporary, and dance charts with such hits as Physical and You’re the One That I Want and won countless hearts as everyone’s favourite Sandy in the blockbuster film version of Grease, has died. She was 73.

Newton-John, a longtime resident of Australia whose sales topped 100 million albums, died Monday at her southern California ranch, John Easterling, her husband, wrote on Instagram and Facebook. “We ask that everyone please respect the family’s privacy during this very difficult time,” the message said.

From 1973-83, Newton-John was among the world’s most popular entertainers. She had 14 top 10 singles just in the US, won four Grammys, and starred with John Travolta in Grease and with Gene Kelly in Xanadu. The fast-stepping Travolta-Newton-John duet, You’re the One That I Want, was one of the era’s biggest songs and has sold more than 15 million copies.

Physical, the bouncy, R-rated smash released in 1981, was No 1 for 10 weeks and was named Billboard’s song of the year despite being banned by some radio stations. An aerobics-friendly promotional clip, filmed in the early years of MTV, won a Grammy for best video.

Co-star of “Grease” John Travolta shared his condolences on Instagram.

“My dearest Olivia, you made all of our lives so much better. Your impact was incredible”, Travolta wrote.