Primary body

In the Solar System, the Sun is the primary for all objects that orbit the star.

A disputed example of a system that may lack a primary is Pluto and its moon Charon.

In 2006, the International Astronomical Union briefly considered a formal definition of the term double planet that could have formally included Pluto and Charon, but this definition was not ratified.

Astronomers have not yet detected any bodies (exomoons) that orbit an exoplanet.

The use of primary to refer to the supermassive black hole at the center of most galaxies has not occurred in scientific journals.