Jacob Benjamin Gyllenhaal (born December 19, 1980) is an Academy Award-nominated American actor. He has appeared in diverse roles since his first lead role in 1999's "October Sky", followed by the 2001 cult hit "Donnie Darko", in which he played a psychologically troubled teen and onscreen brother to his real-life sister, actress Maggie Gyllenhaal. In the 2004 blockbuster "The Day After Tomorrow" he portrayed a student caught in a cataclysmic global cooling event, alongside Dennis Quaid as his father. He then played against type as a frustrated Marine in "Jarhead" (2005). The same year, he won critical acclaim portraying a role that entered popular shorthand as a "gay cowboy" in the controversial but highly acclaimed film "Brokeback Mountain".