Defining Bodies

The international body, founded in 1919, that is the recognised authority for astronomical nomenclature and standards — it defines constellation boundaries, names celestial bodies and their features, and adopts the reference systems and constants used throughout astronomy, including the International Celestial Reference System.

The service that maintains the international celestial and terrestrial reference frames and the parameters linking them — the Earth orientation parameters. The IERS monitors the Earth's rotation and axis, publishes UT1−UTC and polar motion, and announces the leap seconds that keep civil time aligned with the turning Earth.