(Cover) - EN Showbiz - George Clooney is to star alongside Sandra Bullock after replacing Robert Downey Jr. in movie Gravity.

The new film will be directed by Alfonso Cuarn, who has previously helmed Children of Men and Harry Potter and the Prisoner of Azkaban. George will play an astronaut, a part which was originally going to Robert.

Sandra will also play an astronaut in the sci-fi thriller. Her character will face a race against time to return to Earth after an accident occurs while she is in space.

Clooney will replace Downey in the role of team leader of a space station. He and Bullock's character, off working on a shuttle, are the sole survivors when the space station is decimated by the debris field from an exploded asteroid, reports Deadline.

For the last year it had been thought Robert would be taking part, but last month it became clear he was no longer involved. It is thought he couldnt continue with the project due to his busy work schedule.

Sandras role has also been the subject of speculation, with reports in July suggesting Scarlett Johansson had landed the part. Angelina Jolie, Natalie Portman, Marion Cotillard and Blake Lively have also been linked to it.

Production will reportedly begin in April or May next year. (C) Cover Media