"No star is more bright than the moon."

• Incorrect because "more bright" is grammatically incorrect. "Bright" is a one-syllable adjective, so we use "brighter" (comparative form) instead of "more bright."

"No star is brighter then the moon."

• Incorrect because "then" is the wrong word choice.
• "Then" is used for time sequences (e.g., "We ate dinner, then we watched TV").
• "Than" is used for comparisons (e.g., "A car is faster than a bicycle").

"No star is brighter than moon."

• Incorrect because "moon" needs "the" before it.
• The moon is a specific celestial body, so we always use "the moon" in English.