Olivia Newton-John's husband, John Easterling, has penned a heartfelt tribute to the star following her death at the age of 73. 

The singer and actress, who was largely known for her iconic portrayal of Sandy in the 1978 film version of the musical Grease, died Monday, and now Easterling is celebrating her life.

"Our love for each other transcends our understanding. Every day we expressed our gratitude for this love that could be so deep, so real, so natural," Easterling wrote on Instagram. "We never had to 'work' on it. We were in awe of this great mystery and accepted the experience of our love as past, present, and forever."