Unmasking (44) Nysa: Evidence for a trilobate structure

arXiv:2607.25786 · astro-ph.EP, astro-ph.IM · Submitted 2026-07-28 · Read on arXiv

Kate Minker, Anthony Berdeu, Gianluca Li Causi, Josef Hanuš, Michaël Marsset, Al Conrad, Fernando Pedichini, Simone Antoniucci, Piero Vaccari, Nick Moskovitz, Benoit Carry, Tom Polakis, Marin Ferrais, Emmanuël Jehin, Roberto Bonamico, Rhiannon Hicks, Daejhanae Smith, M. Amine Miftah, Ester Marini

astro-ph.EP, astro-ph.IM

Submitted: 2026-07-28

Comments: 12 pages, 8 figures, 5 tables. Accepted as a letter by A&A. Associated videos are available in the journal article, press release, or by contacting K. Minker and provide the best view of the processed data

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

The gist: Context.

Terminology

Adam — 8× in this paper · explained in 2 episodes
Alignment — 4× in this paper · explained in 1 episode
Principal Component Analysis — 3× in this paper
Regularization — 3× in this paper · explained in 3 episodes
Calibration — 2× in this paper · explained in 7 episodes
Core — 2× in this paper · explained in 2 episodes
European Southern Observatory — 2× in this paper
Consistency — 1× in this paper · explained in 3 episodes
Homogeneity — 1× in this paper · explained in 2 episodes
Principal Component Analysis (PCA) — 1× in this paper · explained in 4 episodes
Society of Photo-Optical Instrumentation Engineers — 1× in this paper

Abstract

Context. (44) Nysa is one of the largest known E-type asteroids. Light curve inversion models have indicated that it may have an elongated shape commonly found in large binary systems. Aims. We aimed to identify the morphology and presence of possible satellites orbiting Nysa. Methods. We observed Nysa with the visible-wavelengths adaptive-optics instruments SHARK-VIS and SPHERE/ZIMPOL in order to image the object with the highest possible spatial resolution, and visually identified surface features on the object. A shape model was constructed from these images and photometric light curves using the ADAM code. Results. Imaging revealed a highly unusual morphology with multiple distinct surface features, including two distinct valleys most easily interpreted as colli. A faint satellite was identified in the deconvolution residuals in multiple datasets. Conclusions. We determine that (44) Nysa is a binary system most likely consisting of a contact-trinary or highly-irregular, coherent primary object and a small satellite.

Terminology

Abstract

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