Kilometre-scale Jovian moon characterized for a potential JUICE flyby

arXiv:2607.28357 · astro-ph.EP · Submitted 2026-07-30 · Read on arXiv

Juan Luis Rizos, Jose Maria Gomez-Limon, Yucel Kilic, Altair R. Gomes-Junior, Jose Luis Ortiz, Nicolas Morales, Alvaro Alvarez-Candal, Pasquale Palumbo, Luisa M. Lara, Simon Porter, Benjamin Proudfoot, Evelyn Christiny M. Prais, Jean Marc Christille, Stefano Sartor, Antonio Cabrera, Stefan Geier, Alessia Spolon, Alice Lucchetti, Andrea Soffiantini, Anne Verbiscer, Armin Behrend, Elena Mazzotta Epifani, Jean-Louis Dumont, Luca Zampieri, Mike Skrutskie, Maurizio Pajola, Michel Boutet, Michele Fiori, Raoul Behrend, Stefano Sposetti, Vadim Nikitin, Fabien Cavaille, Jocelyn Serot, Laurent Miralabe, Marc Buie, Mehmed Naim Bagiran, Metin Altan, Mohammad Niaei, Noel Robichon, Orhan Erece, Pierre-Louis Phan, Raphael Lallemand, Suleyman Fisek, Valentin Etienne, Valery Lainey, Yavuz Guney, Yusuf Avcioglu, Francois Poulet, Paul Hartogh, Oliver Witasse, Pablo Santos-Sanz, Julia de Leon, Flavia L. Rommel, Fernando Tinaut-Ruano

astro-ph.EP

Submitted: 2026-07-30

Comments: Published in Nature Astronomy on 24 July 2026

Journal ref: Nature Astronomy (2026)

DOI: 10.1038/s41550-026-02929-z

License: http://creativecommons.org/licenses/by-nc-nd/4.0/

The gist: Jupiter's irregular satellites are thought to be relics of early Solar System planetesimals.

Terminology

Aperture — 17× in this paper · explained in 1 episode
Accuracy — 3× in this paper · explained in 1 episode
Calibration — 3× in this paper · explained in 7 episodes
Bayesian Inference — 2× in this paper · explained in 5 episodes
Degeneracy — 2× in this paper · explained in 3 episodes
Aperture Correction — 1× in this paper · explained in 1 episode
Aperture Photometry — 1× in this paper · explained in 1 episode
Bayesian Framework — 1× in this paper · explained in 3 episodes
Core — 1× in this paper · explained in 2 episodes
European Space Agency — 1× in this paper
Minor Planet Center — 1× in this paper
Point Spread Function — 1× in this paper
Signal-to-noise ratio (SNR) — 1× in this paper · explained in 2 episodes

Abstract

Jupiter's irregular satellites are thought to be relics of early Solar System planetesimals. However, their small sizes, large distances from Earth and close angular proximity to Jupiter make them difficult to characterize remotely. Here we report multi-instrument observations of kilometre-sized Kallichore, the only irregular moon of Jupiter amenable to a close flyby by ESA's Jupiter Icy Moons Explorer (JUICE), whose astrometric and physical properties were still poorly constrained. We used Hubble photometry and astrometry, followed by a ground-based, multi-site stellar occultation campaign and astrometric and photometric observations with the 10.4-m Gran Telescopio Canarias. We reduced Kallichore's orbital uncertainty by up to approximately 80% and determined its shape: an elongated object with a minimum semi-axis ratio of a/b = 1.53 +/- 0.10, an area-equivalent diameter of 3.8 (+2.3/-0.3) km and a dark surface with a geometric albedo of 3.7% (+0.7/-2.2). No close companions were detected. These new constraints provide a viable pathway towards a JUICE flyby once the spacecraft arrives in the Jupiter system in 2031.

Terminology

Abstract

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