you should probably capitalize 'sun', 'moon', and 'earth' when referring to the specific celestial bodies, with the exception of use in metaphors as jbuck points out. do not capitalize 'sun' or 'moon' when referring to any sun or moon other than our own. also do not capitalize 'sun' or 'moon' when talking about the general concept of a sun or mooon. capitalization of 'earth' when it is phrased as 'the earth' is inconsistent and unclear. just pick one way and be consistent, i guess. when referring to our sun and moon, 'the' is mandatory. you cannot say 'We were on Moon" or "Sun released solar flares". here are some examples of how i'd write them: > - **The Sun** is a class G2V star. > - Earth has one **sun**. > - Gliese 581 is a planetary system about 20 light years away from us. Its **sun** is a red dwarf star. > - Life appears to be unique to **Earth**. > - The rocket fell back down to **the Earth** after a few days in low orbit. > - After we dug the hole, we were left with a large pile of **earth**. > - **The Moon** is roughly as wide as Australia. > - Europa is one **moon** of Jupiter.
in: > The rocket fell back down to the Earth after a few days in low orbit. is the 'the' mandotory? I don't think so?