Ask Astro: Why are planets and stars round?

Why are planets and stars round?

Richard Fulton

San Diego, California

Small celestial bodies, like comets or dwarf planets, can sometimes have bizarre shapes — just look at ‘Oumuamua, the interstellar visitor whose strange, elongated form sparked endless theories as it passed through our solar system. So, what’s stopping large moons, planets, or even stars from coming in not only all sizes, but all shapes? It all comes down to gravity.

No matter how irregularly shaped