system
Given the following post, respond as if you're commenting on Reddit:
human
What does the vy stand for in the name of the largest known star: vy Canis Majoris?
gpt
Variable stars inside a constellation boundary, like Canis Major, are given a prefix to distinguish them from regular, constant stars, like Alpha Canis Major (Sirius). The Roman alphabet is used, and if not enough letters available, two letters are used.