Near-Earth asteroids (NEAs) are celestial bodies whose orbits intersect with Earth’s, holding great significance for studying Solar System formation and evolution while posing potential collision hazards to humanity. However, classifying small, newly discovered NEAs remains challenging due to limited observational windows.
Led by researchers from the Purple Mountain Observatory, Chinese Academy of Sciences, the international team conducted a one-year observational campaign from October 2023 to October 2024. Using the Johnson-Cousins BVRI broadband photometric system, they collected data from two telescopes: the Purple Mountain Observatory Yaoan High Precision Telescope (YAHPT, IAU code O49) in China and the Kottamia Astronomical Observatory 1.88 m telescope (IAU code 088) in Egypt. After rigorous data reduction and analysis, the team successfully obtained photometric color indices for 84 NEAs and completed taxonomic classification for 80 of them.
The results show that nearly half (46.3%) of the sampled asteroids belong to the S-complex, 26.3% to the C-complex, 15.0% to the X-complex, and 6% to the D-complex, with the remaining classified as A-type or V-type. Statistical analysis revealed that C/X-complex asteroids are more abundant among smaller NEAs (absolute magnitude H > 17.0), accounting for nearly twice the proportion of larger ones. Additionally, X-complex asteroids tend to have sub-kilometer diameters, while C- and S-complex asteroids show similar distributions across different size ranges.
Orbital parameter analysis indicated that C/D-complex asteroids dominate NEAs with a Jovian Tisserand parameter T J < 3.1, suggesting a potential cometary origin. Notably, NEA (385268) exhibits spectral and dynamical properties consistent with Jupiter-family comets, likely originating from the Themis family via Jupiter’s 2:1 mean-motion resonance. Among 13 potentially hazardous asteroids (PHAs) identified in the sample, C-complex and S-complex asteroids each account for 5, a finding that challenges previous assumptions and highlights new considerations for planetary defense, as C-complex asteroids are more porous, which may reduce the effectiveness of kinetic impact deflection strategies commonly used in planetary defense.
The research provides valuable data for understanding NEA origin and evolution mechanisms, while offering practical guidance for planetary defense planning. Future studies will expand the sample size, focus on fainter NEAs, and incorporate infrared observations to improve classification accuracy.
See the article:
Taxonomic classification of 80 near-Earth asteroids
http://dx.doi.org/10.26464/epp2025080
Earth and Planetary Physics
1-Jan-2026