Hayabusa2 extended mission target asteroid 1998 KY26 is smaller and rotating faster than previously known
Understanding the physical characteristics of small Solar System bodies is important not only for refining formation and evolution models but also for space mission operations. Although several kilometre-sized asteroids have been visited by spacecraft, asteroid 1998 KY<sub>26</sub>-the final target of Hayabusa2#, the extended mission of the Japan Aerospace Exploration Agency's Hayabusa2 spacecraft-will be the first decametre-scale asteroid to be explored in situ. Its small size and rapid spin place it above the upper limit on the rotation rate, indicating it may differ from previously studied bodies. In this work, we conducted a photometric campaign during 1998 KY<sub>26</sub>'s close approach to Earth in 2024, revealing a high optical albedo and Xe-type colours. We determine its spin period to be (5.3516 ± 0.0001) minutes-half the period of earlier estimates. Lightcurve inversion produces retrograde pole solutions in both convex and non-convex shape models. Combined with 1998 Goldstone radar data, these results give a diameter of (11 ± 2) m, three times smaller than previously derived values. The derived cohesive strength levels necessary to keep the structure intact, which is less than 20 Pa, suggest a possibility of the asteroid's rubble pile structure, though this finding does not rule out its monolithic structure. These results can be validated with future James Webb Space Telescope observations. Our comprehensive characterisation can inform the planning of the Hayabusa2# rendezvous in 2031 and helps pave the way for future studies of dark comets.
Authors
- K. Muinonen (ORCID: https://orcid.org/0000-0001-8058-2642)
- Masatoshi Hirabayashi (ORCID: https://orcid.org/0000-0002-1821-5689)
- Adriano Campo Bagatín (ORCID: https://orcid.org/0000-0001-9840-2216)
- A. K. Vivas (ORCID: https://orcid.org/0000-0003-4341-6172)
- Richard Cannon (ORCID: https://orcid.org/0009-0007-5946-8731)
- O. Hainaut (ORCID: https://orcid.org/0000-0001-6952-9349)
- Dagmara Oszkiewicz (ORCID: https://orcid.org/0000-0002-5356-6433)
- Agata Rożek (ORCID: https://orcid.org/0000-0003-2341-2238)
- C. E. Martínez-Vázquez (ORCID: https://orcid.org/0000-0002-9144-7726)
- T. Santana-Ros (ORCID: https://orcid.org/0000-0002-0143-9440)
- Paula Gabriela Benavídez (ORCID: https://orcid.org/0000-0001-6569-0223)
- L. A. M. Benner (ORCID: https://orcid.org/0000-0001-7164-9120)
- M. Brozović (ORCID: https://orcid.org/0009-0007-3493-2139)
- P. Bartczak (ORCID: https://orcid.org/0000-0002-3466-3190)
- M. Micheli (ORCID: https://orcid.org/0000-0001-7895-8209)
- A. Cabrera‐Lavers (ORCID: https://orcid.org/0000-0002-9153-8724)
- Davide Farnocchia (ORCID: https://orcid.org/0000-0003-0774-884X)
- Anne Virkki (ORCID: https://orcid.org/0000-0002-4129-5381)
- Thomas Müller (ORCID: https://orcid.org/0000-0002-0717-0462)
Institutions
- University of Alicante (ES)
- Georgia Institute of Technology (US)
- European Southern Observatory (DE)
- Jet Propulsion Laboratory (US)
- University of Helsinki (FI)
- Max Planck Institute for Extraterrestrial Physics (DE)
- Gemini North Observatory (US)
- Institut Català de Ciències del Clima (ES)
- Royal Observatory (GB)
- Instituto de Astrofísica de Canarias (ES)
- Cerro Tololo Inter-American Observatory (CL)
- Astronomical Observatory (RS)
- European Space Research Institute (IT)
- Adam Mickiewicz University in Poznań (PL)
- Universitat de Barcelona (ES)
- University of Edinburgh (GB)
Publication Details
- Journal
- Nature Communications
- Published
- 2025-09-18
- DOI
- https://doi.org/10.1038/s41467-025-63697-4
- Citations
- 1
- Primary Topic
- Astro and Planetary Science
- Type
- article
- Field-Weighted Citation Impact
- 1.15
Funders
- National Science Foundation
- U.S. Department of Energy
- National Aeronautics and Space Administration
- University of California, Santa Cruz
- University of Pennsylvania
- Ohio State University
- California Institute of Technology
- Universidad de Alicante
- University of Portsmouth
- National Centre for Supercomputing Applications
- University College London
- European Commission
- University of Sussex
- Deutsche Forschungsgemeinschaft
- Eidgenössische Technische Hochschule Zürich
- Conselho Nacional de Desenvolvimento Científico e Tecnológico
- Korea Astronomy and Space Science Institute
- Narodowym Centrum Nauki
- Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
- European Southern Observatory
- Financiadora de Estudos e Projetos
- Ministerio de Ciencia e Innovación
- Universitat de Barcelona
- Ministério da Ciência, Tecnologia, Inovações e Comunicações
- Agencia Nacional de Investigación y Desarrollo
- Institut de Física d'Altes Energies
- Instituto de Astrofísica de Canarias
- University of Illinois at Urbana-Champaign
- Jet Propulsion Laboratory
- Center for Cosmology and Astroparticle Physics, Ohio State University
- Science Mission Directorate
- Kavli Institute for Cosmological Physics, University of Chicago
- Science and Technology Facilities Council
- European Regional Development Fund
- Agencia Estatal de Investigación
- Institut de Ciències del Cosmos
- Integrated Electronics Engineering Center, Binghamton University
- Argonne National Laboratory
- Fermilab
- Lawrence Berkeley National Laboratory
- SLAC National Accelerator Laboratory