Related Clues:

• "The final frontier"
• Sun spot?
• Probe's destination
• The Grand Canyon, e.g.?
• 'Star Trek' venue
• Region beyond the Earth's atmosphere
• 59 Across source, perhaps
• Astronaut's milieu
• Alien territory
• Star's locale
• E.T.'s venue
• UFO's origin
• Distant regions of the universe
• It's far out
• Backyard or patio