Acclaimed British thespian Patrick Stewart, most famously known for captaining the USS Enterprise on the silver screen, has died at 86-years-old.

A statement on his social media accounts reports that the actor passed “following a brief and poignant journey with Alzheimer’s Disease and Lewy Body Dementia.”

A longtime Shakespearean theatre actor, Stewart made his big break on screen as Captain Jean Luc Picard in Star Trek: The Next Generation.

On the big screen, Stewart became a major figure in the world of superheroes with his portrayal of Professor Charles Xavier, or Professor X in the X-Men franchise, and is slated to reprise his role posthumously in Avengers: Doomsday when that premiers in December.