近日，美国麻省理工学院的Artem Y. Burdanov&Julien de Wit及其研究团队取得一项新进展。他们利用JWST实现对十米级主带小行星的观测及对陨石来源的洞察。相关研究成果已于2024年12月9日在国际权威学术期刊《自然》上发表。

据悉，小行星的发现对于旨在防止小行星撞击地球的行星防御工作至关重要，尤其是要防止更频繁的由十米级撞击体引发的百万吨级爆炸。虽然大型小行星（直径≥100公里）自形成以来就一直留在主带中，但小型小行星却经常被输送到近地天体（NEO）星族中。然而，由于缺乏直接的观测限制，它们的尺寸-频率分布（这有助于人们了解近地天体和陨石样本送达地球的情况），在各模型之间存在显著差异。

该研究团队报道了在主带中观测到的最小的138颗小行星（直径小于10米）的发现，这一发现得益于詹姆斯·韦伯空间望远镜（JWST），覆盖小行星发射峰值的红外能力和综合跟踪技术。尽管这些小行星的轨道弧段较小，但研究人员通过利用已知小行星作为代理，限制了这些天体的距离和相位角，从而能够通过辐射测量技术推导出它们的尺寸。

它们的尺寸-频率分布在直径约为100米处出现拐点（对于直径小于和大于约100米的小行星，去偏后的累积斜率分别为q = 2.66 ± 0.60和0.97 ± 0.14），这表明该星族是由碰撞级联驱动的。根据本文考虑的指向几何，这些小行星很可能来自多个小行星族——最有可能是Nysa族、Polana族和Massalia族。通过额外的长时间红外观测，JWST有望偶然探测到天空中数千颗十米级的小行星，从而对各个小行星族和陨石的来源区域进行“原位”探测。

附：英文原文

Title: JWST sighting of decameter main-belt asteroids and view on meteorite sources

Author: Burdanov, Artem Y., de Wit, Julien, Bro, Miroslav, Mller, Thomas G., Hoffmann, Tobias, Ferrais, Marin, Micheli, Marco, Jehin, Emmanuel, Parrott, Daniel, Hasler, Samantha N., Binzel, Richard P., Ducrot, Elsa, Kreidberg, Laura, Gillon, Michal, Greene, Thomas P., Grundy, Will M., Kareta, Theodore, Lagage, Pierre-Olivier, Moskovitz, Nicholas, Thirouin, Audrey, Thomas, Cristina A., Zieba, Sebastian

Issue&Volume: 2024-12-09

Abstract: Asteroid discoveries are essential for planetary-defense efforts aiming to prevent impacts with Earth, including the more frequent megaton explosions from decameter impactors. While large asteroids (≥100km) have remained in the main belt since their formation, small asteroids are commonly transported to the near-Earth object (NEO) population. However, due to the lack of direct observational constraints, their size-frequency distribution —which informs our understanding of the NEOs and the delivery of meteorite samples to Earth—varies significantly among models. Here, we report 138 detections of the smallest asteroids ( 10m) ever observed in the main belt, which were enabled by JWST’s infrared capabilities covering the asteroids’ emission peaks and synthetic tracking techniques. Despite small orbital arcs, we constrain the objects’ distances and phase angles using known asteroids as proxies, allowing us to derive sizes via radiometric techniques. Their size-frequency distribution exhibits a break at ~ 100m (debiased cumulative slopes of q = 2.66 ± 0.60 and   0.97 ± 0.14 for diameters smaller and larger than ~ 100m, respectively), suggestive of a population driven by collisional cascade. These asteroids were sampled from multiple asteroid families —most likely Nysa, Polana and Massalia— according to the geometry of pointings considered here. Through additional long-stare infrared observations, JWST is poised to serendipitously detect thousands of decameter-scale asteroids across the sky, probing individual asteroid families and the source regions of meteorites “in-situ”.

DOI: 10.1038/s41586-024-08480-z

Source: https://www.nature.com/articles/s41586-024-08480-z