1,2,3- 1Zuse Institute Berlin, Berlin, Germany (laeuter@zib.de)
- 2Institute for Theoretical Physics, Johannes Kepler Universität, Linz, Austria
- 3Instituto de Astrofísica de Andalucía, Granada, Spain
The dynamics of a solar system object assumed to be a rigid body can be described by the evolutions of its center-of-mass position and of its rotational state. Close to the surface of a cometary nucleus, volatiles sublimate and expand into the surrounding space. This activity causes non-gravitational forces and torques which correspond to dynamical changes of translational and rotational momenta. Sublimation is related to solar irradiation with the corresponding incoming energy. Within a column of cometary material a thermophysical model describes reradiation of energy, fluxes into subsurface layers, and the transformation into the sublimation process. The curvature and the shape of the nucleus are parameters for the incoming energy and the direction of the forces. Most of these parameters are known with high uncertainties only.
In our study we discuss the temporal evolution of the rotational state of a cometary nucleus and its relation to non-gravitational torques. For rotations close to principal axis state, e.g. in the case of comet 67P/Churyumov-Gerasimenko, observed changes of the rotation state yield constraints for activity in certain regions on the surface, see [3,4]. Other comets rotate in non- principal rotation state, e.g. like comet 103P/Hartley 2, see [1]. Rotational dynamics for the asymmetric rotator with zero torque result in complex signals for the analysis of lightcurves, see [2,5]. We attribute temporal changes in the characterisitic periods of the rotator to acting torques. For the shape of 103P which is close to be symmetric, the decision between short axis mode and long axis mode is linked to high uncertainties.
[1] Belton et al. 2013, Icarus 222, 595-609, doi:10.1016/j.icarus.2012.06.037
[2] Gutiérrez et al. 2003, A&A 406, 1123-1133, doi:10.1051/0004-6361:20030845
[3] Kramer et al. 2019, A&A 630, A3, doi:10.1051/0004-6361/201834349
[4] Läuter&Kramer 2025, A&A 699, A75, doi:10.1051/0004-6361/202553845
[5] Samarasinha et al. 2011, ApJL 734, L3, doi:10.1088/2041-8205/734/1/L3
How to cite: Läuter, M., Kramer, T., Gutiérrez, P., and Attree, N.: Constraints for non-gravitational torque given by lightcurve analysis of comet 103P/Hartley 2, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-760, https://doi.org/10.5194/epsc2026-760, 2026.
