Stellar occultations by Trans-Neptunian Objects

TL;DR

Stellar occultations, enhanced by Gaia's precise predictions, are a versatile tool for studying the shape, atmospheres, rings, and population of distant solar system objects, revealing new features and constraining their properties.

Contribution

This paper reviews recent advances in occultation observations enabled by Gaia, highlighting new discoveries of rings, atmospheres, and population characteristics of Trans-Neptunian Objects.

Findings

Detection of rings around Chariklo, Haumea, and Quaoar.

Monitoring of Pluto's and Triton's atmospheres over decades.

Potential to determine size distribution of km-sized primordial objects.

Abstract

Stellar occultations provide a powerful tool to explore objects of the outer solar system. The Gaia mission now provides milli-arcsec accuracy on the predictions of these events and makes possible observations that were previously unthinkable. Occultations return kilometric accuracies on the three-dimensional shape of bodies irrespective of their geocentric distances, with the potential of detecting topographic features along the limb. From the shape, accurate values of albedo can be derived, and if the mass is known, the bulk density is pinned down, thus constraining the internal structure and equilibrium state of the object. Occultations are also extremely sensitive to tenuous atmospheres, down to the nanobar level. They allowed the monitoring of Pluto's and Triton's atmospheres in the last three decades, constraining their seasonal evolution. They may unveil in the near future atmospheres around other remote bodies of the solar system. Since 2013, occultations have led to the surprising discovery of ring systems around the Centaur object Chariklo, the dwarf planet Haumea and the large trans-Neptunian object Quaoar, while revealing dense material around the Centaur Chiron. This suggests that rings are probably much more common features than previously thought. Meanwhile, they have raised new dynamical questions concerning the confining effect of resonances forced by irregular objects on ring particles. Serendipitous occultations by km-sized trans-Neptunian or Oort objects has the potential to provide the size distribution of a population that suffered few collisions until now, thus constraining the history of primordial planetesimals in the 1-100 km range.