Speaker
Description
Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. Modern astrometry has been entirely revolutionized by the ESA space missions Hipparcos and Gaia. With its last release, DR3, and the next December 2026 DR4, Gaia allowed milli-arcsec (mas) precision on the positions, parallaxes and proper motions of about 2 billion stars down to a faint limiting magnitude of ~20. However, Gaia suffers from severe detector saturation for the brightest sources (G < 5), strongly limiting the astrometric precision of these sources.
A possible way to overcome this problem is based on the analysis of historical astrometric catalogues with a long-term baseline (>150 years). Building upon a methodology successfully developed for Santini’s Paduan Catalogues, we demonstrate how this cross-matching and re-reduction procedure can be systematically extended to Giuseppe Piazzi’s pioneering stellar Catalogues and other nineteenth-century meridian circles observations (i.e. Bessel, Argelander, etc.).
This integrated pipeline directly incorporates these historical stellar positions within a unified, common astrometric framework alongside Hipparcos and Gaia data, after carefully modeling and mitigating the intrinsic instrumental biases and systematic errors of early meridian circles. By executing a continuous, multi-epoch linear regression across this extended secular baseline, we derive highly robust proper motion components. The direct comparison between these secular kinematic tracks and modern space measurements naturally reveals subtle proper motion anomalies, long-period orbital curvatures, or unexpected kinematic variations. This approach effectively transforms legacy catalogues into active scientific assets capable of capturing complex, long-term stellar dynamics.