The phrase "celestial objects" refers to things in space, like planets, stars, moons, and galaxies. It includes anything that exists or moves in the sky outside of Earth. Full definition
«In order to find them, we combed through images of billions of celestial objects millions of times fainter than what the naked eye can see.» (ibtimes.com)
It has also sent research craft to study planets and other celestial objects in our solar system, including Pluto. (sciencenewsforstudents.org)
These struts block some of the surface of the dish, scattering some of the incoming radio waves from celestial objects under study. (public.nrao.edu)