Orbits of very distant asteroid satellites^★

¹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice cedex 4, France
² IMCCE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ Paris 06, Univ. Lille, 75014 Paris, France
³ Astronomical Institute AS CR, Fričova 298, Ondřejov, Czech Republic
⁴ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, Postfach 1312, 85741 Garching, Germany
⁵ Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15–17, 1121 Budapest, Hungary
⁶ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁷ Large Binocular Telescope Observatory, University of Arizona, Tucson, AZ 85721, USA
⁸ Department of Earth & Environmental Sciences, Michigan State University, East Lansing, MI 48824, USA
⁹ European Southern Observatory (ESO), Alonso de Cordova 3107, 1900 Casilla Vitacura, Santiago, Chile
¹⁰ Southwest Research Institute, 1301 Walnut St. #400, Boulder, CO 80302, USA
¹¹ Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
¹² Sugarloaf Mountain Observatory, South Deerfield, MA, USA
¹³ Observatoire OPERA, 33820 Saint-Palais, France
¹⁴ Astronomical Institute of the Slovak Academy of Sciences, SK-05960 Tatranská Lomnica, The Slovak Republic
¹⁵ Belgrade Astronomical Observatory, Volgina 7, 11060 Belgrade 38, Serbia
¹⁶ Sonoita Research Observatory, 77 Paint Trail, Sonoita, AZ 85637, USA
¹⁷ Space sciences, Technologies & Astrophysics Research (STAR) Institute, University of Liege, Liege, Belgium
¹⁸ Modra Observatory, Department of Astronomy, Physics of the Earth, and Meteorology, FMPI UK, Mlynská dolina, Bratislava 84248, Slovakia
¹⁹ Department of Astronomy, Physics of the Earth, and Meteorology, FMPI, Comenius University, Mlynská Dolina F1, Bratislava 84248, Slovakia
²⁰ Institute of Astronomy of V.N. Karazin Kharkiv National University, Kharkiv 61022, Sumska Str. 35, Ukraine
²¹ Observatoire La Souchère, 69510 Soucieu-en-Jarrest, France
²² Via Capote Observatory, Thousand Oaks, CA 91320, USA
²³ Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK
²⁴ Currently at NOIRLab/Gemini Observatory, 950 N Cherry Ave, Tucson, AZ, 85719, USA
²⁵ Lowell Observatory, 1400 W. Mars Hill Rd., Flagstaff, AZ 86001, USA
²⁶ Steward Observatory, N420, Department of Astronomy, University of Arizona, 933 N. Cherry Ave. Tucson, AZ 85721, USA

^★★ Corresponding author: kate.minker@oca.eu

Received: 14 June 2024
Accepted: 18 March 2025

Abstract

Context. The very wide binary asteroid (VWBA) population is a small subset of the population of known binary and multiple asteroids made of systems with very widely orbiting satellites and long orbital periods, on the order of tens to hundreds of days. The origin of these systems is debatable, and most members of this population are poorly characterized.

Aims. We aim to develop orbital solutions for some members of the VWBA population, allowing us to constrain possible formation pathways for this unusual population.

Methods. We compiled all available high-angular-resolution imaging archival data of VWBA systems from large ground- and space-based telescopes. We measured the astrometric positions of the satellite relative to the primary at each epoch and analyzed the dynamics of the satellites using the Genoid genetic algorithm. Additionally, we used a NEATM thermal model to estimate the diameters of two systems, and we modeled the orbit of Litva’s inner satellite using photometric light curve observations.

Results. We determine the effective diameters of binary systems (17246) Christophedumas and (22899) Alconrad to be 4.7 ± 0.4 km and 5.2 ± 0.3 km, respectively. We determine new orbital solutions for five systems, (379) Huenna, (2577) Litva, (3548) Eurybates, (4674) Pauling, and (22899) Alconrad. We find a significantly eccentric (e = 0.30) best-fit orbital solution for the outer satellite of (2577) Litva, moderately eccentric (e = 0.13) solutions for (22899) Alconrad, and a nearly circular solution for (4674) Pauling (e = 0.04). We also confirm previously reported orbital solutions for (379) Huenna and (3548) Eurybates.

Conclusions. It is unlikely that BYORP expansion could be solely responsible for the formation of VWBAs, as only (4674) Pauling matches the necessary requirements for active BYORP expansion. It is possible that the satellites of these systems were formed through YORP spin-up and then later scattered onto very wide orbits. Additionally, we find that some members of the population are unlikely to have formed satellites through YORP spin-up, and a collisional formation history is favored. In particular, this applies to VWBAs within large dynamical families, such as (22899) Alconrad and (2577) Litva, or large VWBA systems such as (379) Huenna and NASA’s Lucy mission target (3548) Eurybates.