LOS ANGELES, Calif. — Jeanne Cooper, who portrayed Katherine Chandler on “The Young and the Restless” for 40 years, died today of an undisclosed illness at age 84.

Her death was announced on Twitter and Facebook by her son, actor Corbin Bernsen, who is best known for his work on “L.A. Law” and has been providing his online followers with updates on his mother’s health for weeks.

“My mother passed away this morning just a short time ago, peaceful with my sister by her side, in her sleep,” Bernsen wrote on his Facebook page.

“I was going to visit this afternoon, thought I had time. Reminder to self — time is a precious thing.”

“I too am at peace, however. I said my goodbyes several times over during the last few weeks,” he wrote. “… And while her light finally gave into the wind that gives flight to all our journeys, there will always be a glimmer left behind by what she stood for. … I will certainly dedicate what remains of my life to continue her purpose of honesty, equality, humility, empathy and love.”

Cooper joined “The Young and the Restless” in 1973, but also made a pair of crossover appearances on the soap “The Bold and the Beautiful.” She even made a pair of guest shots on “L.A. Law,” portraying Bernsen’s mother.

She made a series of appearances on various television shows in the 1950s and 1960s, including “The Adventures of Kit Carson,” “Highway Patrol,” “Maverick,” “The Tall Man,” “Surfside 6,” “Have Gun – Will Travel,” “Rawhide,” “The Untouchables” and “Mike Hammer.” She also made multiple appearances on “Perry Mason,” “Walt Disney’s Wonderful World of Color” and “Ironside” before landing her soap opera job.

She and ex-husband Harry Bernsen, a television producer, had three children — Corbin, Collin and Caren Bernsen.

Cooper received 10 Daytime Emmy Award nominations during her career, winning once in 2008. She received a lifetime achievement award in 2004, and was nominated twice for Primetime Emmy Awards, including once for “L.A. Law.”