Related Clues:

• Theme of this puzzle
• Astronomer's sighting
• Hale-Bopp, e.g.
• Close in films
• Temporary skylight?
• Shower participant?
• Senator who made the rounds
• Falling star
• Senator John
• Kitchen cleanser
• Doomsday cause, maybe
• Earth threatener
• Enterprise, e.g.
• Common cleanser
• One of 39-Across