2024-12-09 マサチューセッツ工科大学(MIT)
An artist’s illustration of NASA’s James Webb Space Telescope revealing, in the infrared, a population of small main-belt asteroids.
Image: Ella Maru and Julien de Wit
＜関連情報＞
- https://news.mit.edu/2024/mit-astronomers-find-smallest-asteroids-ever-detected-main-belt-1209
- https://www.nature.com/articles/s41586-024-08480-z
JWSTがメインベルトの小惑星を視認、隕石源についての見解も示す JWST sighting of decameter main-belt asteroids and view on meteorite sources
Artem Y. Burdanov,Julien de Wit,Miroslav Brož,Thomas G. Müller,Tobias Hoffmann,Marin Ferrais,Marco Micheli,Emmanuel Jehin,Daniel Parrott,Samantha N. Hasler,Richard P. Binzel,Elsa Ducrot,Laura Kreidberg,Michaël Gillon,Thomas P. Greene,Will M. Grundy,Theodore Kareta,Pierre-Olivier Lagage,Nicholas Moskovitz,Audrey Thirouin,Cristina A. Thomas & Sebastian Zieba
Nature Published:09 December 2024
DOI:https://doi.org/10.1038/s41586-024-08480-z
We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.
Abstract
Asteroid discoveries are essential for planetary-defense efforts aiming to prevent impacts with Earth1, including the more frequent2 megaton explosions from decameter impactors3−6. While large asteroids (≥100 km) have remained in the main belt since their formation7, small asteroids are commonly transported to the near-Earth object (NEO) population8,9. 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 models10−14. Here, we report 138 detections of the smallest asteroids (⪆ 10 m) ever observed in the main belt, which were enabled by JWST’s infrared capabilities covering the asteroids’ emission peaks15 and synthetic tracking techniques16−18. 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 ~ 100 m (debiased cumulative slopes of q = − 2.66 ± 0.60 and − 0.97 ± 0.14 for diameters smaller and larger than ~ 100 m, 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 families19 and the source regions of meteorites13,14 “in-situ”.
