Bellatrix is a relatively unique and uncommon word that may not have many direct synonyms, but there are plenty of related words that can be used in its place. Some possible synonyms for Bellatrix could include words like star, celestial body, galaxy, cosmos, universe, heaven, firmament, sky, space, or even astronomy or astrophysics. These synonyms all have something to do with space or celestial bodies, which is why they may be appropriate words to use instead of Bellatrix. However, it is also worth noting that Bellatrix is a specific star in the Orion constellation, so some of these synonyms may be more apt than others depending on the context.