Opposition effect of Trojan asteroids

Shevchenko, V. G.; Belskaya, I. N.; Slyusarev, I.; Krugly, Yu. N.; Chiorny, V. G.; Gaftonyuk, N. M.; Donchev, Z.; Ivanova, V.; Ibrahimov, M.; Ehgamberdiev, S. A.; Молотов, И. Е.

doi:10.1016/j.icarus.2011.11.001

Cited by 40 publications

(33 citation statements)

References 21 publications

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“…At phase angles less than 5°, an opposition surge is observed; this is now understood as due to coherent backscattering, as it is stronger for higher albedo surfaces (Muinonen et al 2002). Phase curves for Trojan asteroids are linear down to phase angles of ~0.1-0.2° (Shevchenko et al 2012). This linear behavior differs dramatically from the sharp opposition spikes seen in several Centaurs, and is similar to what is observed for dark outer Main Belt and Hilda asteroids (Shevchenko et al 2012).…”

Section: Rotational States and Phase Curvesmentioning

confidence: 95%

“…Phase curves for Trojan asteroids are linear down to phase angles of ~0.1-0.2° (Shevchenko et al 2012). This linear behavior differs dramatically from the sharp opposition spikes seen in several Centaurs, and is similar to what is observed for dark outer Main Belt and Hilda asteroids (Shevchenko et al 2012). Shevchenko et al (2012) attribute the absence of a strong opposition surge to the low albedos of Trojan asteroids.…”

Section: Rotational States and Phase Curvesmentioning

confidence: 95%

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The Complex History of Trojan Asteroids

Emery¹,

Marzari²,

Morbidelli³

et al. 2015

Asteroids IV

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The Trojan asteroids provide a unique perspective on the history of Solar System. As a large population of small bodies, they record important gravitational interactions and dynamical evolution of the Solar System. In the past decade, significant advances have been made in understanding physical properties, and there has been a revolution in thinking about the origin of Trojans. The ice and organics generally presumed to be a significant part of Trojan compositions have yet to be detected directly, though low density of the binary system Patroclus (and possibly low density of the binary/moonlet system Hektor) is consistent with an interior ice component. By contrast, fine-grained silicates that appear to be similar to cometary silicates in composition have been detected, and a color bimodality may indicate distinct compositional groups among the Trojans. Whereas Trojans had traditionally been thought to have formed near 5 AU, a new paradigm has developed in which the Trojans formed in the proto-Kuiper Belt, and they were scattered inward and captured in the Trojan swarms as a result of resonant interactions of the giant planets. Whereas the orbital and population distributions of current Trojans are consistent with this origin scenario, there are significant differences between current physical properties of Trojans and those of Kuiper Belt objects. These differences may be indicative of surface modification due to the inward migration of objects that became the Trojans, but understanding of appropriate modification mechanisms is poor and would benefit from additional laboratory studies. Many open questions remain, and the future promises significant strides in our understanding of Trojans. The time is ripe for a spacecraft mission to the Trojans, to turn these objects into geologic worlds that can be studied in detail to unravel their complex history.Comment: Chapter for Asteroids IV book (UA Press), accepted for publication, 33 pages, 10 figure

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Section: Rotational States and Phase Curvesmentioning

confidence: 95%

Section: Rotational States and Phase Curvesmentioning

confidence: 95%

The Complex History of Trojan Asteroids

Emery¹,

Marzari²,

Morbidelli³

et al. 2015

Asteroids IV

View full text Add to dashboard Cite

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“…Absolute magnitudes, H R , were computed from the apparent magnitudes using the inverse square law and the HG formalism (Bowell et al 1989) with assumed phase angle parameter G = 0.15, as is appropriate for dark surfaces. The phase darkening coefficients are unmeasured, however, introducing some uncertainty into H R , particularly if the Trojans should show significant opposition surge (although available evidence from the Jovian Trojans indicates that they do not; Shevchenko et al 2012). Values of H R are quoted only to one decimal place in recognition of this phase function uncertainty.…”

Section: Observationsmentioning

confidence: 99%

The Trojan Color Conundrum

Jewitt

2018

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The Trojan asteroids of Jupiter and Neptune are likely to have been captured from original heliocentric orbits in the dynamically excited ("hot") population of the Kuiper belt. However, it has long been known that the optical color distributions of the Jovian Trojans and the hot population are not alike. This difference has been reconciled with the capture hypothesis by assuming that the Trojans were resurfaced (for example, by sublimation of near-surface volatiles) upon inward migration from the Kuiper belt (where blackbody temperatures are ∼40

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“…The model has experienced several improvements with more physical description since its introduction in the 1980s (Hapke 1993(Hapke , 2002(Hapke , 2008(Hapke , 2012, which is the reason that there are several different versions. For a comet that is expected to be composed of dark phases rich in carbon, the coherent-backscattering mechanism (Shevchenko & Belskaya 2010;Shevchenko et al 2012) is not expected to play a major role. For the single-particle-phase function, we adopted the single-term of the Henyey-Greenstein (HG) form (Hapke 2012), with one asymmetry parameter, g. A negative g value represents backscattering, a positive one forward scattering, and g = 0 stands for isotropic scattering.…”

Section: Hapke Model On Disk-averaged Photometrymentioning

confidence: 99%

Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

Fornasier

Hasselmann

Barucci

et al. 2015

A&A

215

147

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Context. The Rosetta mission of the European Space Agency has been orbiting the comet 67P/Churyumov-Gerasimenko (67P) since August 2014 and is now in its escort phase. A large complement of scientific experiments designed to complete the most detailed study of a comet ever attempted are onboard Rosetta. Aims. We present results for the photometric and spectrophotometric properties of the nucleus of 67P derived from the OSIRIS imaging system, which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). The observations presented here were performed during July and the beginning of August 2014, during the approach phase, when OSIRIS was mapping the surface of the comet with several filters at different phase angles (1.3• -54• ). The resolution reached up to 2.1 m/px. Methods. The OSIRIS images were processed with the OSIRIS standard pipeline, then converted into I/F radiance factors and corrected for the illumination conditions at each pixel using the Lommel-Seeliger disk law. Color cubes of the surface were produced by stacking registered and illumination-corrected images. Furthermore, photometric analysis was performed both on disk-averaged photometry in several filters and on disk-resolved images acquired with the NAC orange filter, centered at 649 nm, using Hapke modeling. Results. The disk-averaged phase function of the nucleus of 67P shows a strong opposition surge with a G parameter value of −0.13 ± 0.01 in the HG system formalism and an absolute magnitude H v (1, 1, 0) = 15.74 ± 0.02 mag. The integrated spectrophotometry in 20 filters covering the 250−1000 nm wavelength range shows a red spectral behavior, without clear absorption bands except for a potential absorption centered at ∼290 nm that is possibly due to SO 2 ice. The nucleus shows strong phase reddening, with disk-averaged spectral slopes increasing from 11%/(100 nm) to 16%/(100 nm) in the 1.3• −54• phase angle range. The geometric albedo of the comet is 6.5 ± 0.2% at 649 nm, with local variations of up to ∼16% in the Hapi region. From the disk-resolved images we computed the spectral slope together with local spectrophotometry and identified three distinct groups of regions (blue, moderately red, and red). The Hapi region is the brightest, the bluest in term of spectral slope, and the most active surface on the comet. Local spectrophotometry shows an enhancement of the flux in the 700−750 nm that is associated with coma emissions.

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Opposition effect of Trojan asteroids

Cited by 40 publications

References 21 publications

The Complex History of Trojan Asteroids

The Complex History of Trojan Asteroids

The Trojan Color Conundrum

Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

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