You could use orb: Our great orb in the sky is our greatest sources of light. I am not sure of anyone would use it to describe the moon or not unless specifically distinguished as night-sky.

When talking about space and the solar system, the sun is often referred to as "Sol" ("sun" in Latin). It's a proper name, and so is capitalized and does not take "the." - "It is 4.37 light years from Alpha Centauri to Sol."

you can call it “yellow dwarf” 🤭

the sun/the Sun: The large bright object in the sky that gives us light and heat, and around which the Earth moves solar: relating to the sun

“Solar” means coming from the sun. You cannot say “The solar is very bright today!” You can say “It’s a great idea to use solar energy as much as possible, since the sun is so strong here.” I’m a teacher on this platform, let me know if you would like to take formal lessons on advanced topics!