Radar Imaging of Binary Near-Earth Asteroid (66391) 1999 KW4

Ostro, S. J.; Margot, Jean-Luc; Benner, L. A. M.; Giorgini, Jon D.; Scheeres, Daniel J.; Fahnestock, Eugene G.; Broschart, Stephen B.; Bellerose, Julie; Nolan, M. C.; Magri, C.; Pravec, Petr; Scheirich, P.; Rose, Randall L.; Jurgens, R. F.; Jong, E. M. De; Suzuki, Shigeru

doi:10.1126/science.1133622

Cited by 286 publications

(253 citation statements)

References 17 publications

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“…The overall shape that corresponds to the first pole solution could evoke similarity to the spinning top shapes of some nearEarth primaries (e.g., asteroid (66391) 1999 KW 4 , Ostro et al 2006), however, the equatorial ridge in our case is not that obvious and symmetric. On the other hand, the second shape model is more angular and seems to us rather less realistic.…”

Section: Shape Model and Rotation Statementioning

confidence: 79%

Near-Earth asteroid (3200) Phaethon: Characterization of its orbit, spin state, and thermophysical parameters

Hanuš

Delbò

Vokrouhlický

et al. 2016

A&A

110

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Context. The near-Earth asteroid (3200) Phaethon is an intriguing object: its perihelion is at only 0.14 au and is associated with the Geminid meteor stream. Aims. We aim to use all available disk-integrated optical data to derive a reliable convex shape model of Phaethon. By interpreting the available space-and ground-based thermal infrared data and Spitzer spectra using a thermophysical model, we also aim to further constrain its size, thermal inertia, and visible geometric albedo. Methods. We applied the convex inversion method to the new optical data obtained by six instruments and to previous observations. The convex shape model was then used as input for the thermophysical modeling. We also studied the long-term stability of Phaethon's orbit and spin axis with a numerical orbital and rotation-state integrator.Results. We present a new convex shape model and rotational state of Phaethon: a sidereal rotation period of 3.603958(2) h and ecliptic coordinates of the preferred pole orientation of (319 • , −39 • ) with a 5 • uncertainty. Moreover, we derive its size (D = 5.1 ± 0.2 km), thermal inertia (Γ = 600 ± 200 J m −2 s −1/2 K −1 ), geometric visible albedo (p V = 0.122 ± 0.008), and estimate the macroscopic surface roughness. We also find that the Sun illumination at the perihelion passage during the past several thousand years is not connected to a specific area on the surface, which implies non-preferential heating.

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Section: Shape Model and Rotation Statementioning

confidence: 79%

Near-Earth asteroid (3200) Phaethon: Characterization of its orbit, spin state, and thermophysical parameters

Hanuš

Delbò

Vokrouhlický

et al. 2016

A&A

110

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“…In this section we test seven different asteroid shape models, all of them consisting in thousands of triangular facets. The asteroids we test are Toutatis, 1998 KY26, Castalia, Golevka (shape models from [Neese 2004]), the asteroid 1992 SK, from [Busch et al 2006], the asteroid Nereus, from [Brozovic et al 2009] and the asteroid 1999 KW4, from [Ostro et al 2006].…”

Section: Tests On Asteroidsmentioning

confidence: 99%

Averaged rotational dynamics of an asteroid in tumbling rotation under the YORP torque

Cicalò

Scheeres²

2010

Celest Mech Dyn Astr

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The secular effect of YORP torque on the rotational dynamics of an asteroid in non-principal axis rotation is studied. The general rotational equations of motion are derived and approximated with an illumination function expanded up to second order. The resulting equations of motion can be averaged over the fast rotation angles to yield secular equations for the angular momentum, dynamic inertia and obliquity. We study the properties of these secular equations and compare results to previous research. Finally, an application to several real asteroid shapes is made, in particular we study the predicted rotational dynamics of the asteroid Toutatis, which is known to be in a non-principal axis state.

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“…It is caused by the recoil effect from the anisotropic reflection and emission of solar radiation and thermal photons, respectively (Rubincam 2000). This process is responsible for many observed phenomena in asteroid science (Slivan 2002;Vokrouhlický et al 2003;Ostro et al 2006;Vokrouhlický & Nesvorný 2008;Pravec et al 2010), and was detected on the very small, fast spinning Based in part on observations collected at the European Southern Observatory, Chile, under programme ID: 185.C-1033. Table 2 is available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A48 near-Earth asteroid (54509) YORP (Lowry et al 2007;Taylor et al 2007).…”

Section: Introductionmentioning

confidence: 99%

The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up

Lowry

Weissman

Duddy

et al. 2014

A&A

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Context. Near-Earth asteroid (25143) Itokawa was visited by the Hayabusa spacecraft in 2005, resulting in a highly detailed shape and surface topography model. This model has led to several predictions for the expected radiative torques on this asteroid, suggesting that its spin rate should be decelerating. Aims. To detect changes in rotation rate that may be due to YORP-induced radiative torques, which in turn may be used to investigate the interior structure of the asteroid. Methods. Through an observational survey spanning 2001 to 2013 we obtained rotational lightcurve data at various times over the last five close Earth-approaches of the asteroid. We applied a polyhedron-shape-modelling technique to assess the spin-state of the asteroid and its long term evolution. We also applied a detailed thermophysical analysis to the shape model determined from the Hayabusa spacecraft. Results. We have successfully measured an acceleration in Itokawa's spin rate of dω/dt = (3.54 ± 0.38) × 10 −8 rad day −2 , equivalent to a decrease of its rotation period of ∼45 ms year −1 . From the thermophysical analysis we find that the centre-of-mass for Itokawa must be shifted by ∼21 m along the long-axis of the asteroid to reconcile the observed YORP strength with theory. Conclusions. This can be explained if Itokawa is composed of two separate bodies with very different bulk densities of 1750 ± 110 kg m −3 and 2850 ± 500 kg m −3 , and was formed from the merger of two separate bodies, either in the aftermath of a catastrophic disruption of a larger differentiated body, or from the collapse of a binary system. We therefore demonstrate that an observational measurement of radiative torques, when combined with a detailed shape model, can provide insight into the interior structure of an asteroid. Futhermore, this is the first measurement of density inhomogeneity within an asteroidal body, that reveals significant internal structure variation. A specialised spacecraft is normally required for this.

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Radar Imaging of Binary Near-Earth Asteroid (66391) 1999 KW4

Cited by 286 publications

References 17 publications

Near-Earth asteroid (3200) Phaethon: Characterization of its orbit, spin state, and thermophysical parameters

Near-Earth asteroid (3200) Phaethon: Characterization of its orbit, spin state, and thermophysical parameters

Averaged rotational dynamics of an asteroid in tumbling rotation under the YORP torque

The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up

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