古行星能够用肉眼看到七个天体之一，水星、金星、月球、太阳、火星、木星和土星，古代天文学家认为它在天空中围绕着固定的地球和固定的恒星中旋转
One of the seven celestial bodies, Mercury, Venus, the moon, the sun, Mars, Jupiter, and Saturn, visible to the naked eye and thought by ancient astronomers to revolve in the heavens about a fixed Earth and among fixed stars.
水星上面过于干燥，并且缺乏氧气。
Mercury is too dry and poor in oxygen.
内行星明亮的半圆月球、水星或金星其一半被照亮的现象
The phase of the moon, Mercury, or Venus when half of the disk is illuminated.
我们太阳系的行星有水星、金星、地球、火星、木星、土星、天王星和海王星。
The planets of our solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
