The Celestial Sphere is a concept in astronomy that refers to an imaginary sphere of stars that surrounds the Earth. It is also known as the HEAVENS, which is a 7-letter word that can be found in a crossword puzzle. The Celestial Sphere is studied in Astronomy, a 9-letter word that can also be found in a crossword puzzle. The Celestial Sphere is also sometimes referred to as an ORB, a 3-letter word that can be found in a crossword puzzle.