Jon Hamm is in negotiations to star opposite Natalie Portman in Fox Searchlight’s “Pale Blue Dot,” sources tell Variety.

“Fargo” and “Legion” creator Noah Hawley is directing from a script by Brian C. Brown and Elliott DiGuiseppi. Reese Witherspoon, who was attached to star at one point, will produce with Bruna Papandrea.

“Pale Blue Dot” follows a successful female astronaut who, after coming back home from a mission in space, starts to unravel when confronted by her seemingly perfect life. The film explores the theory that astronauts who spend long periods of time in space lose their sense of reality when they return home.

Hamm will play Portman’s fellow astronaut who she aggressively pursues after returning to Earth.

With “Legion” wrapped and Hawley’s other FX series, “Fargo,” not shooting until next year, production on “Pale Blue Dot” is expected to start in the spring.

Hamm, best known for his iconic role as Don Draper on AMC’s “Mad Men,” has taken on more movies since the show ended in 2015. He most recently starred in “Marjorie Prime” and also had a scene-stealing role as a bank robber in Edgar Wright’s “Baby Driver.” His thriller “Beirut” recently bowed to solid reviews at the Sundance Film Festival.

Hamm is repped by CAA, Forward Entertainment, and Sloane, Offer, Weber & Dern.