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Title: NEAR-INFRARED SPECTROSCOPY OF TROJAN ASTEROIDS: EVIDENCE FOR TWO COMPOSITIONAL GROUPS

Abstract

The Trojan asteroids, a very substantial population of primitive bodies trapped in Jupiter's stable Lagrange regions, remain quite poorly understood. Because they occupy these orbits, the physical properties of Trojans provide a unique perspective on the chemical and dynamical processes that shaped the Solar System. The current study was therefore undertaken to investigate surface compositions of these objects. We present 66 new near-infrared (NIR; 0.7-2.5 {mu}m) spectra of 58 Trojan asteroids, including members of both the leading and trailing swarms. We also include in the analysis previously published NIR spectra of 13 Trojans (3 of which overlap with the new sample). This data set permits not only a direct search for compositional signatures, but also a search for patterns that may reveal clues to the origin of the Trojans. We do not report any confirmed absorption features in the new spectra. Analysis of the spectral slopes, however, reveals an interesting bimodality among the NIR data. The two spectral groups identified appear to be equally abundant in the leading and trailing swarms. The spectral groups are not a result of family membership; they occur in the background, non-family population. The average albedos of the two groups are the same within uncertaintiesmore » (0.051 {+-} 0.016 and 0.055 {+-} 0.016). No correlations between spectral slope and any other physical or orbital parameter are detected, with the exception of a possible weak correlation with inclination among the less-red spectral group. The NIR spectral groups are consistent with a similar bimodality previously suggested among visible colors and spectra. Synthesizing the present results with previously published properties of Trojans, we conclude that the two spectral groups represent objects with different intrinsic compositions. We further suggest that whereas the less-red group originated near Jupiter or in the main asteroid belt, the redder spectral group originated farther out in the Solar System. If this suggestion is correct, the Trojan swarms offer the most readily accessible large reservoir of Kuiper Belt material as well as a unique reservoir for the study of material from the middle part of the solar nebula.« less

Authors:
;  [1]
  1. Earth and Planetary Science Department and Planetary Geosciences Institute, University of Tennessee, Knoxville, TN 37996 (United States)
Publication Date:
OSTI Identifier:
21583268
Resource Type:
Journal Article
Journal Name:
Astronomical Journal (New York, N.Y. Online)
Additional Journal Information:
Journal Volume: 141; Journal Issue: 1; Other Information: DOI: 10.1088/0004-6256/141/1/25; Journal ID: ISSN 1538-3881
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABSORPTION SPECTROSCOPY; ALBEDO; ASTEROIDS; INCLINATION; INFRARED SPECTRA; JUPITER PLANET; ORBITS; SOLAR NEBULA; SOLAR SYSTEM; NEBULAE; PLANETS; SORPTION; SPECTRA; SPECTROSCOPY

Citation Formats

Emery, J P, Burr, D M, and Cruikshank, D. P., E-mail: jemery2@utk.edu. NEAR-INFRARED SPECTROSCOPY OF TROJAN ASTEROIDS: EVIDENCE FOR TWO COMPOSITIONAL GROUPS. United States: N. p., 2011. Web. doi:10.1088/0004-6256/141/1/25.
Emery, J P, Burr, D M, & Cruikshank, D. P., E-mail: jemery2@utk.edu. NEAR-INFRARED SPECTROSCOPY OF TROJAN ASTEROIDS: EVIDENCE FOR TWO COMPOSITIONAL GROUPS. United States. https://doi.org/10.1088/0004-6256/141/1/25
Emery, J P, Burr, D M, and Cruikshank, D. P., E-mail: jemery2@utk.edu. 2011. "NEAR-INFRARED SPECTROSCOPY OF TROJAN ASTEROIDS: EVIDENCE FOR TWO COMPOSITIONAL GROUPS". United States. https://doi.org/10.1088/0004-6256/141/1/25.
@article{osti_21583268,
title = {NEAR-INFRARED SPECTROSCOPY OF TROJAN ASTEROIDS: EVIDENCE FOR TWO COMPOSITIONAL GROUPS},
author = {Emery, J P and Burr, D M and Cruikshank, D. P., E-mail: jemery2@utk.edu},
abstractNote = {The Trojan asteroids, a very substantial population of primitive bodies trapped in Jupiter's stable Lagrange regions, remain quite poorly understood. Because they occupy these orbits, the physical properties of Trojans provide a unique perspective on the chemical and dynamical processes that shaped the Solar System. The current study was therefore undertaken to investigate surface compositions of these objects. We present 66 new near-infrared (NIR; 0.7-2.5 {mu}m) spectra of 58 Trojan asteroids, including members of both the leading and trailing swarms. We also include in the analysis previously published NIR spectra of 13 Trojans (3 of which overlap with the new sample). This data set permits not only a direct search for compositional signatures, but also a search for patterns that may reveal clues to the origin of the Trojans. We do not report any confirmed absorption features in the new spectra. Analysis of the spectral slopes, however, reveals an interesting bimodality among the NIR data. The two spectral groups identified appear to be equally abundant in the leading and trailing swarms. The spectral groups are not a result of family membership; they occur in the background, non-family population. The average albedos of the two groups are the same within uncertainties (0.051 {+-} 0.016 and 0.055 {+-} 0.016). No correlations between spectral slope and any other physical or orbital parameter are detected, with the exception of a possible weak correlation with inclination among the less-red spectral group. The NIR spectral groups are consistent with a similar bimodality previously suggested among visible colors and spectra. Synthesizing the present results with previously published properties of Trojans, we conclude that the two spectral groups represent objects with different intrinsic compositions. We further suggest that whereas the less-red group originated near Jupiter or in the main asteroid belt, the redder spectral group originated farther out in the Solar System. If this suggestion is correct, the Trojan swarms offer the most readily accessible large reservoir of Kuiper Belt material as well as a unique reservoir for the study of material from the middle part of the solar nebula.},
doi = {10.1088/0004-6256/141/1/25},
url = {https://www.osti.gov/biblio/21583268}, journal = {Astronomical Journal (New York, N.Y. Online)},
issn = {1538-3881},
number = 1,
volume = 141,
place = {United States},
year = {Sat Jan 15 00:00:00 EST 2011},
month = {Sat Jan 15 00:00:00 EST 2011}
}