Related Clues:

• Saturn, for one
• Astronomer's sighting
• 5-Down, for example
• Part of a belt
• Vulcan, for one
• Jupiter, e.g.
• Saturn or Mercury
• See 31-Across
• Mars, e.g.
• Revolver?
• Miniplanet
• Mars or Mercury
• Space rock
• It has solar heating
• Mercury or Saturn