Piers Morgan reacts to John Travolta's moving tribute to Olivia Newton-John

Singer Olivia Newton-John, who soared to the top of the world's pop music charts in the 1970s and 1980s with such tunes as "I Honestly Love You" and "Physical" and starred in the hit movie musical "Grease," died on Monday at age 73 at her home in Southern California.

The death of the British-born, Australian-raised performer was announced on her Instagram account, saying she "passed away peacefully" at her ranch home "surrounded by family and friends."

she cemented her acclaim by co-starring with John Travolta in "Grease," the 1978 film that would become one of the most popular musicals in Hollywood history.

In the film, set in the 1950s, Newton-John's prim character, Sandy, has a summer fling with Danny, the "greaser" portrayed by Travolta, but the relationship falls apart over cultural differences. In the end they reconcile as their roles reverse, with Danny cleaning up his act, and Sandy making a striking appearance in a tight, black leather outfit.

Travolta, 68, addressed a tribute to his co-star on Instagram, saying her "impact was incredible."

"My dearest Olivia, you made all of our lives so much better," the actor wrote. "I love you so much. We will see you down the road and we will all be together again. Yours from the first moment I saw you and forever! your Danny, your John!"

TV presenter Piers Morgan shared Travolta's heartfelt tribute to his Twitter account with a crying face emoji.