The Gaia Celestial Reference Frame (Gaia-CRF2) has been defined by means of the Gaia Data Release 2 measurements for 556 869 quasars. Within the measuring accuracy of Gaia, these quasars show no significant proper motions, as they are simply too distant. These quasars are also observable from the ground with interferometric radio telescopes, giving positional accuracies compatible with Gaia data, though currently the number of quasars measured by Gaia is about 100 times higher than those for which good positional data has been obtained with radio telescopes. Ultimately, the combination of the radio telescope and Gaia measurements provides a positional and proper motion reference system at milli-arcsecond accuracy level, which can be used in a wide range of applications, from pointing extremely large telescopes (https://en.wikipedia.org/wiki/Extremely_large_telescope ) on ground or in space (https://www.jwst.nasa.gov/ ) to serving as reference system in accurate reconstruction of orbits for solar system objects. More on the Gaia Celestial Reference Frame can be found at https://www.cosmos.esa.int/web/gaia/gaiadr2_rf .
Page last updated: 09 August 2018