Tomorrow, Thursday Feb. 7, starting at 10:30 a.m.,
The chat will feature video of Hadfield, and Shatner will be on the phone. You can watch it live at the Canadian Space Agency's website.
The chat was spawned by this Twitter exchange between Shatner (who plays a future Starship captain on TV) and Hadfield (who commands the International Space Station RIGHT NOW).
@williamshatner Yes, Standard Orbit, Captain. And we're detecting signs of life on the surface.
— Chris Hadfield (@Cmdr_Hadfield) January 3, 2013
The Internet tells us that the MBB at the end of Shatner's message means: "My, Best Bill."
Hadfield has been tweeting from space since he arrived there, on Dec. 21. Here's an epic roundup of all the tweets between Hadfield and the Star Trek crew.