*Julia Roberts, Goldie Hawn, Gabriel Byrne, Forest Whitaker and Mariel Hemingway have signed on to deliver feature-length documentaries for the Oprah Winfrey Network, which is scheduled to debut in January as a joint venture of Winfrey and Discovery Communications.

Roberts’ Red Om Films will exec produce “Extraordinary Moms,” an exploration of motherhood, while Whitaker will narrate and exec produce an in-depth look at Angola, the infamous maximum security prison in Louisiana.

“Searching for Happiness,” an inquiry into the motivations and secrets behind happiness, features Hawn as host, narrator and exec producer. Byrne will exec produce “Tent City,” an examination of Nashville’s homeless population. “Seven Suicides” follows Hemingway as she probes into her own family legacy of suicide and depression.

Each two-hour picture, including the previously announced “Family Affair” and original acquisitions “Life 2.0” and “Sons of Perdition,” aim to showcase the work of emerging cinematic voices for mainstream audiences.