Siderophobia

Siderophobia is the morbid phobia (fear) of celestial stars.

Causes
There are not many known causes for this fear, as it isn't very well-known in itself.

A potential cause of this fear is the belief that following the stars will lead to your demise, undoing, death or some kind of bad event.

Some others think stars are a sign of bad luck.

It could also link to childhood experiences and other such things. For example, a child could witness a shooting star while very young and think it will kill them or loved ones, leading to the overall phobia and the lasting avoidance with looking at the night sky.

Another source could be the immense number of stars, which might cause fear in more anxious people, especially kids of a young age. Some more subtle causes might include: it makes you feel insignificant when you look up at the immense size of the night sky; worrying that the stars might move or crash down on you suddenly; realizing how dangerous stars are up close, and noticing how far away stars really are and how maybe not everything is as it should seem based on that reason.

A final thing that could cause this fear might be the belief that each orb in the nighttime sky represents a dead person's soul. This is presumably the potential cause that makes the most sense. It could bring out the realization of how many dead people there are, which may provoke a chain reaction leading to the thought of how short life is.

Extra

 * In Aztec mythology, the Tzitzimitl were star demons that were believed to descend from the sky to eat people if the New Fire ceremony failed.
 * The Greek word "Sideros", meaning iron and not star, often stirs confusion. This quote will be embedded into this page to clear things up, and the original text can be found in the comments.
 * "The stem 'sider-' is from Latin sīdus 'a constellation; a star' (Latin sidereus is an adjectival form of sīdus meaning 'pertaining to a constellation, or to a star or stars'). 'Sider-' combined with the Latin-Greek connective vowel '-o-' is graphically identical to the stem 'sidero-' which is from the Greek word σίδηρος (sideros), meaning 'iron'. It is theorized that the two stems are etymologically related, as the sparks formed by striking iron appear similar to the stars in the heavens, yet that is but speculation. Lexical sources indicate the stem 'sidero-' can be used for either 'star' or 'iron', thus siderophobia is a valid term for the 'fear of stars'. It may possibly erroneously, but possibly validly yet confusingly used, as a term for the 'fear of iron.' The fear of iron, though, can be identified as ferrumphobia, from the Latin word 'ferrum', meaning 'iron'." -A Fandom user, posted 11/13/2015.