A1 Refereed original research article in a scientific journal
Rapid-Response Characterization of Near-Earth Asteroid 2024 YR4 During a Torino Scale 3 Alert
Authors: Devogèle, Maxime; Hainaut, Olivier R.; Micheli, Marco; Pravec, Petr; Cano, Juan Luis; Ocaña, Francisco; Conversi, Luca; Moskovitz, Nicholas; de León, Julia; Gray, Zuri; Granvik, Mikael; Fedorets, Grigori; de Micas, Jules Bourdelle; Ieva, Simone; Dotto, Elisabetta; Beuden, Tracie; Fuls, Carson; Kareta, Theodore; Bagnulo, Stefano; Barucci, Maria Antonella; Birlan, Mirel; Farina, Andrea; Hornoch, Kamil; Fatka, Petr; Kušnirák, Peter; Ferri, Francesca; Fulchignoni, Marcello; Lazzarin, Monica; La Forgia, Fiorangela; Epifani, Elena Mazzotta; Mura, Alessandra; Perna, Davide; Bendjoya, Philippe; Rivet, Jean-Pierre; Cellino, Alberto
Publisher: Springer Science and Business Media LLC
Publication year: 2026
Journal: Journal of the Astronautical Sciences
Article number: 31
Volume: 73
Issue: 2
ISSN: 0021-9142
eISSN: 2195-0571
DOI: https://doi.org/10.1007/s40295-025-00550-2
Publication's open availability at the time of reporting: No Open Access
Publication channel's open availability : Partially Open Access publication channel
Web address : https://doi.org/10.1007/s40295-025-00550-2
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/523215966
Self-archived copy's version: Final draft
On 27 December 2024, near-Earth object (NEO) 2024 was discovered by the ATLAS survey and identified as a virtual impactor. A few weeks later, it eventually reached level 3 on the Torino Scale and was the first and only asteroid to be ever classified at that level. Here we report an intensive observational campaign combining time-series photometry in the visible, broadband visible and near-infrared colors, and low-resolution visible reflectance spectroscopy to assess its physical properties. Fourier analysis of the lightcurves yields a synodic rotation period of min, placing 2024 among the fast rotators, even if such rotation is common for objects of similar H magnitude. Its visible and near-infrared colors and spectra are most consistent with an Sq or K taxonomic classification, though some ambiguity remains. Finally, its phase curve exhibits a notably shallow slope (), from which we derive an absolute magnitude of mag. After color correction and taking into account other models for the phase function, we report an absolute magnitude of mag. These characterizations, rotation period, taxonomy, and surface properties, would have been crucial for risk assessment and mitigation planning had the initially high impact probability scenario been confirmed, underscoring the importance for planetary defense of a rapid, coordinated international response.
Funding information in the publication:
Based on observations collected at the European Southern Observatory under ESO programmes 113.2690.002 and 114.28HT.001. The authors are grateful to ESO for the extremely fast response time for our DDT proposal. The observations at the 1.54m Danish telescope at La Silla Observatory in Chile and the work at Ondřejov were supported by the Praemium Academiae award (no. AP2401) from the Academy of Sciences of the Czech Republic. Based on observations made with the Nordic Optical Telescope, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias. The NOT data were obtained under program ID P68-803). Based on observations collected at the Telescopio Nazionale Galileo (TNG, A50TAC31), operated on the island of La Palma by the Centro Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. The 4.3m Lowell Discovery Telescope observations have been obtained thanks to the support of the NASA YORPD grant 80NSSC21K1328 awarded to the Mission Accessible Near-Earth Object Survey (MANOS). The NEOPOPS observations were funded by a programme of the European Union and implemented by ESA (agreement No.4000147191/25/D/MRP).
