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Published September 15, 2025 | Version Published
Journal Article Open

Estimates of rotation periods for Jupiter Trojans with the Zwicky Transient Facility photometric lightcurves

Creators

  • 1. ROR icon University of Washington
  • 2. ROR icon California Institute of Technology
  • 3. Rubin Observatory, 950 Cherry Ave., Tucson, 85719, AZ, USA
  • 4. ROR icon University of British Columbia
  • 5. ROR icon Eureka Scientific
  • 6. ROR icon Infrared Processing and Analysis Center

Abstract

We present new rotational period estimates for 216 Jupiter Trojans using photometric data from the Zwicky Transient Facility (ZTF), including 80 Trojans with previously unknown periods. Our analysis reveals rotation periods ranging from 4.6 h to 447.8 h. These results support the existence of a spin barrier for Trojans larger than 10 km, with periods clustering between 4 and 4.8 h. This spin barrier is roughly twice as long as that observed for main-belt asteroids, suggesting that Jupiter Trojans have significantly lower bulk densities, likely due to a higher fraction of ices and volatile materials in their composition. We identify three new Trojans with reliable rotation periods near the spin barrier, doubling the number of known Trojans in this critical period range. Using these results, we estimate a mean density of ∼0.52g/cm³ for rubble-pile Trojans. Our findings contribute to the growing body of evidence that many Trojans are rubble-pile bodies with distinct physical properties compared to main-belt asteroids. Looking forward, we anticipate that forthcoming data from the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will provide rotational period estimates for several hundred thousand Trojans, down to objects as small as 1 km, enabling a more detailed investigation of their rotational properties and internal structure.

Copyright and License

© 2025 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).

Acknowledgement

The data used in this paper were obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the ZTF project. ZTF is supported by the National Science Foundation, United States under Grants No. AST-1440341 and AST-2034437 and a collaboration including current partners Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum, Northwestern University and former partners the University of Washington, Los Alamos National Laboratories, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW.

Data Availability

This GitHub repository ( https://github.com/ZhuofuLi/ZTF-Jupiter-Trojan-Rotation-Periods) provides rotation period analysis for 216 Jupiter Trojans using ZTF data. It includes a summary table with periods, amplitudes, diameters, and reliability flags. Light curve plots and data are available upon request.
 

Additional Information

In preparing this work, we utilized ChatGPT to refine the grammar and enhance the flow of paragraphs in this paper. Following the use of this tool, we thoroughly reviewed and edited the content as necessary, and we assume full responsibility for the final publication.

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2504.15530 (arXiv)
Is supplemented by
Dataset: https://github.com/ZhuofuLi/ZTF-Jupiter-Trojan-Rotation-Periods (URL)

Funding

National Science Foundation
AST-1440341
National Science Foundation
AST-2034437

Dates

Accepted
2025-04-15
Available
2025-05-11
Available online
Available
2025-05-14
Version of record

Caltech Custom Metadata

Caltech groups
Center for Data-Driven Discovery (CDDD), Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility, Division of Physics, Mathematics and Astronomy (PMA)
Publication Status
Published