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Reference frame · ICRS

The International Celestial Reference System

The modern, fixed reference frame for the sky, defined by the positions of hundreds of distant quasars whose motion is undetectable. It replaced frames tied to the slowly-shifting equinox with one anchored to some of the most distant objects known — the standard to which all precise astronomical positions are now referred.

Highlights

  • The sky's frame, fixed to distant quasars

Across celestial mechanics

Knowledge connections

Sources

The primary and reference sources this topic draws on.

  • IAUInternational Astronomical Union

    Official naming, definitions, constellation boundaries, and astronomical nomenclature.