Rotation periods of asteroids serendipitously observed by the NASA/Kepler K2 mission

¹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France
² V.N. Karazin Kharkiv National University, Kharkiv, Ukraine
³ Department of Aerospace Engineering, Grainger College of Engineering/Department of Astronomy/NCSA, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
⁴ IMCCE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ Paris 06, Univ. Lille, 75014 Paris, France
⁵ Aix Marseille Univ, CNRS, CNES, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France

^★ Corresponding author: alexey.v.sergeyev@gmail.com

Received: 6 February 2025
Accepted: 8 September 2025

Abstract

Context. Understanding the rotational periods of asteroids is crucial for gaining insights into their internal structures, compositions, and collisional histories. NASA’s Kepler Space Telescope, during its K2 extension (2014-2018), serendipitously observed numerous asteroids while surveying the ecliptic plane, providing a unique photometric dataset.

Aims. By analyzing photometric data from the K2 mission, we aimed to determine the rotational periods of asteroids that crossed Kepler’s field of view, focusing on objects with an apparent magnitude of 19 or brighter that appeared in the Kepler target pixel files at least ten times.

Methods. We developed an algorithm to identify asteroid crossings in the Kepler data and extract photometric light curves. The Lomb–Scargle periodogram method was employed to determine the rotational periods from the extracted light curves due to its robustness in handling unevenly sampled data. Noise and systematic errors were mitigated through photometric corrections using co-trending basis vectors.

Results. We extracted and analyzed 4,596 light curves from 2,418 asteroids observed during the Kepler/K2 mission. This allowed us to compute rotation periods for 559 asteroids. We found that 375 of these asteroids had previously known periods. The rotation periods determined for 295 of the asteroids in this study agree with existing asteroid rotation periods from the literature, validating our approach. We report new rotation periods and their light curve amplitudes for 184 asteroids, expanding the catalog of known asteroid rotation periods.

Conclusions. The analysis of rotation periods from the Kepler K2 mission data has provided valuable insights into the physical characteristics of main-belt asteroids. Our results are consistent with existing data and expand the catalog of known asteroid rotation periods. These findings contribute to our understanding of asteroid dynamics and will aid future research in planetary science and asteroid exploration.