The word "un-celestial" refers to something that is not related to the heavens or sky. Its antonyms, therefore, would be words that directly relate to the sky and the celestial world. Words such as astronomical, heavenly, celestial, ethereal, and cosmic can be considered antonyms for "un-celestial". These words describe elements that are connected to the sky, stars, planets, and the universe. They bring a sense of wonder, awe, and mystery that is often associated with the celestial world. Therefore, if you want to describe something that is directly related to the heavens, you could use any of these antonyms instead of "un-celestial".