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Reference frame · J2000.0

The J2000 Epoch

The standard reference epoch of modern astronomy — noon on 1 January 2000, in Terrestrial Time. Because the sky's apparent frame drifts with precession, coordinates and orbital elements are stated for a fixed epoch, and J2000.0 is the one in near-universal use.

Highlights

  • The reference instant of modern astronomy

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.