Farewell to one of America's sweethearts: Olivia Newton-John dies at age 73

"Dame Olivia Newton-John (73) passed away peacefully this morning at her Ranch in Southern California, surrounded by family and friends," her husband, John Easterling, reported on the actress' official Facebook page. He added: "We ask everyone to please respect the family's privacy during this very difficult time."

Olivia Newton-John, who became world famous for her role in Grease (1978), had an extensive career as an actress and singer, and also distinguished herself for her involvement in the fight against cancer and her environmental and animal activism. Her memorable on-screen partner, John Travolta, has said goodbye to her with a heartfelt message posted on his Instagram account: