New photometric observations of asteroids (1862) Apollo and (25143) Itokawa – an analysis of YORP effect

Ďurech, Josef; Vokrouhlický, David; Kaasalainen, M.; Weissman, P. R.; Lowry, S. C.; Beshore, E. C.; Higgins, David; Krugly, Yu. N.; Shevchenko, V. G.; Gaftonyuk, N. M.; Choi, Young Jun; Kowalski, R. A.; Larson, S. M.; Warner, Brian D.; Marshalkina, A. L.; Ibrahimov, M.; Молотов, И. Е.; Michałowski, Tadeusz; Kitazato, K.

doi:10.1051/0004-6361:200809663

Cited by 50 publications

(27 citation statements)

References 25 publications

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“…Using the relative shape model dimensions, this effective diameter implies a maximum equatorial diameter, A, of 2.43 ± 0.13 km, which can be compared against that determined by Doppler radar measurements. Combining Apollo's observed Doppler radar bandwidth (Ostro et al 2002) with the light-curve-derived pole orientation, which has an uncertainty of ±7 • in arc (Kaasalainen et al 2007;Durech et al 2008a), gives Apollo's maximum equatorial diameter as 2.07 ± 0.07 km (see Table 1 for the radar observation geometry). The ATPM fit therefore overestimates the maximum equatorial diameter by a factor of 1.17 ± 0.07.…”

Section: Results and Shape Optimisationmentioning

confidence: 99%

A thermophysical analysis of the (1862) Apollo Yarkovsky and YORP effects

Rozitis

Duddy

Green

et al. 2013

A&A

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Context. The Yarkovsky effect, which causes orbital drift, and the YORP effect, which causes changes in rotation rate and pole orientation, play important roles in the dynamical and physical evolution of asteroids. Near-Earth asteroid (1862) Apollo has strong detections of both orbital semimajor axis drift and rotational acceleration. Aims. We produce a unified model that can accurately match both observed effects using a single set of thermophysical properties derived from ground-based observations, and we determine Apollo's long term evolution. Methods. We use light-curve shape inversion techniques and the advanced thermophysical model (ATPM) on published light-curve, thermal-infrared, and radar observations to constrain Apollo's thermophysical properties. The derived properties are used to make detailed predictions of Apollo's Yarkovsky and YORP effects, which are then compared with published measurements of orbital drift and rotational acceleration. The ATPM explicitly incorporates 1D heat conduction, shadowing, multiple scattering of sunlight, global self-heating, and rough surface thermal-infrared beaming in the model predictions. Results. We find that ATPM can accurately reproduce the light-curve, thermal-infrared, and radar observations of Apollo, and simultaneously match the observed orbital drift and rotational acceleration using: a shape model with axis ratios of 1.94:1.65:1.00, an effective diameter of 1.55 ± 0.07 km, a geometric albedo of 0.20 ± 0.02, a thermal inertia of 140 +140 −100 J m −2 K −1 s −1/2 , a highly rough surface, and a bulk density of 2850 +480 −680 kg m −3 . Using these properties we predict that Apollo's obliquity is increasing towards the 180 • YORP asymptotic state at a rate of 1.5 +0.3 −0.5 degrees per 10 5 yr. Conclusions. The derived thermal inertia suggests that Apollo has loose regolith material resting on its surface, which is consistent with Apollo undergoing a recent resurfacing event based on its observed Q-type spectrum. The inferred bulk density is consistent with those determined for other S-type asteroids, and suggests that Apollo has a fractured interior. The YORP effect is acting on a much faster timescale than the Yarkovsky effect and will dominate Apollo's long term evolution. The ATPM can readily be applied to other asteroids with similar observational data sets.

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Section: Results and Shape Optimisationmentioning

confidence: 99%

A thermophysical analysis of the (1862) Apollo Yarkovsky and YORP effects

Rozitis

Duddy

Green

et al. 2013

A&A

Self Cite

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“…In contrast tǒ Durech et al (2008b), we assumed a logarithmic spacing with the 768 × 2 k rule. Thus, starting from the 11E mesh of 1 572 864 triangles, we stepped down to 1E with 1536 faces and similarly so for kUR and kQ.…”

Section: Simplified Meshesmentioning

confidence: 99%

The YORP effect on 25 143 Itokawa

Breiter

Bartczak

Czekaj

et al. 2009

A&A

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Context. The asteroid 25143 Itokawa is one of the candidates for the detection of the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect in the rotation period. Previous studies were carried out up to the 196 608 facets triangulation model and were not able to provide a good theoretical estimate of this effect, raising questions about the influence of the mesh resolution and the centre of mass location on the evolution the rotation period. Aims. The YORP effect on Itokawa is computed for different topography models up to the highest resolution Gaskell mesh of 3 145 728 triangular faces in an attempt to find the best possible YORP estimate. Other, lower resolution models are also studied and the question of the dependence of the rotation period drift on the density distribution inhomogeneities is reexamined. A comparison is made with 433 Eros models possessing a similar resolution. Methods. The Rubincam approximation (zero conductivity) is assumed in the numerical simulation of the YORP effect in rotation period. The mean thermal radiation torques are summed over triangular facets assuming Keplerian heliocentric motion and uniform rotation around a body-fixed axis.Results. There is no evidence of YORP convergence in Gaskell model family. Differently simplified meshes may converge quickly to their parent models, but this does not prove the quality of YORP computed from the latter. We confirm the high sensitivity of the YORP effect to the fine details of the surface for 25 143 Itokawa and 433 Eros. The sensitivity of the Itokawa YORP to the centre of mass shift is weaker than in earlier works, but instead the results prove to be sensitive to the spin axis orientation in the body frame. Conclusions. Either the sensitivity of the YORP effect is a physical phenomenon and all present predictions are questionable, or the present thermal models are too simplified.

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“…In Fujiwara et al (2006), Yano et al (2006) and Miyamoto et al (2007) detailed descriptions of the morphology of the Itokawa "neck" region are given which find that loose regolith has migrated into this region from neighboring locations with higher elevation. The remaining surface of the asteroid is found to be rather rocky and evidently devoid of a finer regolith covering.…”

Section: Representative Corrections For Itokawamentioning

confidence: 99%

“…Despite this success, the YORP effect for the one small NEA whose shape and mass is best characterized, the asteroid Itokawa (Gaskell et al, 2006a(Gaskell et al, , 2006b, has not been detected yet (Durech et al, 2008), despite predictions that YORP should have been evident by now . 1 The non-detection of the YORP effect for Itokawa raises a number of interesting modeling questions about the details of the YORP effect.…”

Section: Introductionmentioning

confidence: 99%

Effect of density inhomogeneity on YORP: The case of Itokawa

Scheeres¹,

Gaskell

2008

Icarus

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The effect of density inhomogeneity on the YORP effect for a given shape model is investigated. A density inhomogeneity will cause an offset between the center of figure and the center of mass and a reorientation of the principal axes away from those associated with the shape alone. Both of these effects can alter the predicted YORP rate of change in angular velocity and obliquity. We apply these corrections to the Itokawa shape model and find that its YORP angular velocity rate is sensitive to offsets between its center of mass and center of figure, with a shift on the order of 15 m being able to change the sign of the YORP effect for that asteroid. Given the non-detection of YORP for Itokawa as of 2008, this can shed light on the density distribution within that body. The theory supports a shift of the asteroid center of mass towards Itokawa's neck region, where there is an accumulation of finer gravels, or towards the asteroid's "Head" region. Detection of the YORP effect for Itokawa should provide some strong constraints on its density distribution. This theory could also be applied to asteroids visited by future spacecraft to constrain density inhomogeneities.

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New photometric observations of asteroids (1862) Apollo and (25143) Itokawa – an analysis of YORP effect

Cited by 50 publications

References 25 publications

A thermophysical analysis of the (1862) Apollo Yarkovsky and YORP effects

A thermophysical analysis of the (1862) Apollo Yarkovsky and YORP effects

The YORP effect on 25 143 Itokawa

Effect of density inhomogeneity on YORP: The case of Itokawa

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