The Darkest Hour actress Olivia Thirlby is set to join the cast of Christopher Nolans biographical feature film Oppenheimer.The film is based on the Pulitzer Prize-winning book American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer' by Kai Bird and the late Martin J. Sherwin. However, details with regards to her role are not yet clear, reports Deadline'.The film will document the life of Manhattan Project leader J. Robert Oppenheimer (essayed by Cillian Murphy), the theoretical physicist whose work on the Manhattan Project led to the creation of the atomic bomb.As per Deadline', Thirlby joins a star-studded ensemble that also includes Emily Blunt, Florence Pugh, Robert Downey Jr., Matt Damon, Rami Malek, Benny Safdie, Josh Hartnett, Dane DeHaan, Jack Quaid, Matthew Modine, Dylan Arnold, David Krumholtz, Alden Ehrenreich, David Dastmalchian, Olli Haaskivi, Jason Clarke, James D'Arcy, Michael Angarano, Guy Burnet, Danny Deferrari, Matthias Schweigh fer, Gary Oldman, Harrison Gilbertson, Emma Dumont, Devon Bostick, Trond Fausa, Christopher Denham and Josh Zuckerman.Nolan is directing from his own screenplay and producing alongside Emma Thomas and Atlas Entertainment's Charles Roven. 'Deadline' reports that the production is taking place in New Mexico, California and New Jersey, and the film is set to arrive in cinemas on July 21, 2023.