Gravitational astrometry from within the solar system

Abstract

Mission like Gaia (ESA, launched in 2013) requires to treat gravity properly when compiling microsecond stellar catalogues. This will open the opportunity to put in practice methods of Relativistic Astrometry mainly devoted to model the celestial sphere with the percepts of General Relativity (GR) and promotes the use of highly accurate astrometry to test locally fundamental physics. Gaia will be able to carry out general relativistic tests by means of both global and differential astrometric measurements. Global tests will be done through the full astrometric reconstruction of the celestial sphere, while the differential experiments will be implemented in the form of repeated Eddington-like measurements. After one century, Gaia will perform the largest experiment in GR ever made with astrometric methods (since 1919): a relativistic all-sky reconstruction which includes also QSO at different redshifts. Moreover, at zero redshift, dealing with local cosmology, accurate absolute motions of stars within our Galaxy will provide tests on current cosmological models via the detections of cosmological signatures in the disk and halo.