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Published September 2017 | Submitted + Published
Journal Article Open

0.7–2.5μm Spectra of Hilda Asteroids


The Hilda asteroids are primitive bodies in resonance with Jupiter whose origin and physical properties are not well understood. Current models posit that these asteroids formed in the outer solar system and were scattered along with the Jupiter Trojans into their present-day positions during a chaotic episode of dynamical restructuring. In order to explore the surface composition of these enigmatic objects in comparison with an analogous study of Trojans, we present new near-infrared spectra (0.7–2.5 μm) of 25 Hilda asteroids. No discernible absorption features are apparent in the data. Synthesizing the bimodalities in optical color and infrared reflectivity reported in previous studies, we classify 26 of the 28 Hildas in our spectral sample into the so-called less-red and red sub-populations and find that the two sub-populations have distinct average spectral shapes. Combining our results with visible spectra, we find that Trojans and Hildas possess similar overall spectral shapes, suggesting that the two minor body populations share a common progenitor population. A more detailed examination reveals that while the red Trojans and Hildas have nearly identical spectra, less-red Hildas are systematically bluer in the visible and redder in the near-infrared than less-red Trojans, indicating a putative broad, shallow absorption feature between 0.5 and 1.0 μm. We argue that the less-red and red objects found in both Hildas and Trojans represent two distinct surface chemistries and attribute the small discrepancy between less-red Hildas and Trojans to the difference in surface temperatures between the two regions.

Additional Information

© 2017 American Astronomical Society. Received 2017 May 12. Accepted 2017 July 27. Published 2017 August 23. The NASA Infrared Telescope Facility is operated by the University of Hawaii. This research was supported by grant NNX09AB49G from the NASA Planetary Astronomy Program. We also acknowledge an anonymous referee for helpful comments and suggestions that helped improve the manuscript.

Attached Files

Published - Wong_2017_AJ_154_104.pdf

Submitted - 1707.09064.pdf


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August 21, 2023
October 17, 2023