Justin Louis and Jamil Walker Smith Jamil Walker Smith

The new Stargate's universe is expanding. On the heels of the announcement that Trainspotting's Robert Carlye will front the new Sci Fi Channel series (playing Dr. Nicholas Rush), TVGuide.com has learned exclusively that Justin Louis and Jamil Walker Smith have joined the nascent cast.

Louis (Hidden Hills) will play Colonel Everett Young, an experienced and married Stargate team leader, while Smith (Hey, Arnold!) will portray Sr. Sgt. Ronald Greer, a Marine with an explosive temper...and a mysterious past to account for it.

Brad Wright and Robert Cooper (both of SG-1 and Atlantis) will serve as executive producers and writers on the new series, which will kick off with a two-hour movie event this fall.

"SGU" (as we shall apparently call it) follows a band of soldiers, scientists and civilians who are forced through a Stargate when their base comes under attack. Alas, they emerge aboard an ancient ship, which is locked on an unknown course and cannot return to Earth.