1. 光年   outer space   satellite   planet   light years   Hint Half-n-half Clue   2. 重力   light years   meteorite   galaxy   gravity   Half-n-half Clue   3. 行星   moon   planet   Earth   meteor   Half-n-half Clue   4. 地球   moon   meteor   Earth   meteorite   Half-n-half Clue   5. 宇航员   astronomer   meteorite   universe   astronaut   Half-n-half Clue   6. 飞星   astronaut   meteor   solar system   light years   Half-n-half Clue   7. 彗星   orbit   Earth   comet   asteroid   Half-n-half Clue