The solar system

◼ Gaia surveys the Solar System

Gaia regularly collects data on the positions of asteroids and other Solar System bodies, as part of its precious harvest.

The astrometry of known asteroids (once they have been identified through an input catalog), adjusted over the five-year duration of the nominal mission, has resulted in a recent publication [Gaia collaboration, David et al., 2023] showing the quality of orbits obtained for around 150,000 asteroids.

If we consider Gaia data alone, the precision resulting from orbit adjustments is not only 20 to 50 times better than that obtained from the previous catalog (DR3), but is comparable to data obtained from the ground over several decades, or even hundreds of years. This shows the progress achieved by increasing the time range of observations based on very high-precision astrometry.

This augurs well for the final version of the orbit catalog, which will be based on a ten-year time span, doubling the number of asteroids, complemented by comets and satellites, thus improving our knowledge of the small bodies of the Solar System.

◼ New asteroids with unexpected characteristics

Gaia continuously identifies Solar System objects that are mobile relative to the stars in its field of observation. The motion of these objects is compared with that of objects in a reference catalog.

When no object in this catalog matches the observation, an alert is sent out to ground-based observatories to validate and track the new object.

The Gaia-FUN-SSO ground tracker has thus been able to validate the detection of more than 500 objects, some of them new, others already known but not referenced because their orbits are very poorly known.

It has been shown that these non-referenced objects are on orbits that are notably more inclined and more eccentric than the average characteristics of referenced objects in the ASTORB catalog [Carry et al., 2021].

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