【新航道之词汇解析】天文学astronomy:·银河系Galaxy ·太阳系solar system ·恒星fixed star ·行星 planet ·水星Mercury ·金星Venus ·地球Earth ·火星Mars ·木星Jupiter ·土星Saturn ·卫星satellite ·彗星comet ·流星meteor ·轨道orbit ·公转revolve ·自传rotate ·大气层 atmosphere