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

Lowry, S.C., Weissman, P.R., Duddy, S.R., Rozitis, B., Fitzsimmons, A., Green, S.F., Hicks, M.D., Snodgrass, C., Wolters, S.D., Chesley, S.R., and others. (2014) The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up. Astronomy and Astrophysics, 562 . (A48) 1-9. ISSN 0004-6361. E-ISSN 1432-0746. (doi:10.1051/0004-6361/201322602) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. (Contact us about this Publication)
Official URL
http://dx.doi.org/10.1051/0004-6361/201322602

Abstract

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 dÏ?/dt = (3.54 ± 0.38) Ã? 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. © ESO, 2014.

Item Type: Article
DOI/Identification number: 10.1051/0004-6361/201322602
Additional information: Unmapped bibliographic data: C7 - A48 [EPrints field already has value set] LA - English [Field not mapped to EPrints] J2 - Astron. Astrophys. [Field not mapped to EPrints] AD - Centre for Astrophysics and Planetary Science, School of Physical Sciences (SEPnet), University of Kent, Canterbury, CT2 7NH, United Kingdom [Field not mapped to EPrints] AD - Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, United States [Field not mapped to EPrints] AD - Planetary and Space Sciences, Department of Physical Sciences, Open University, Milton Keynes, MK7 6AA, United Kingdom [Field not mapped to EPrints] AD - Astrophysics Research Centre, Queens University Belfast, Belfast, BT7 1NN, United Kingdom [Field not mapped to EPrints] AD - Max Planck Institute for Solar System Research, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany [Field not mapped to EPrints] AD - Isaac Newton Group of Telescopes, 38700 Santa Cruz de la Palma, Canary Islands, Spain [Field not mapped to EPrints] DB - Scopus [Field not mapped to EPrints]
Uncontrolled keywords: Methods: observational, Minor planets asteroids: individual: (25143) Itokawa, Radiation mechanisms: thermal, Techniques: photometric, Interior structure, Internal structure, Methods:observational, Minor planets, Near-earth asteroids, Radiation mechanisms: thermal, Rotation period, Techniques: photometric, Spacecraft, Asteroids
Subjects: Q Science > QB Astronomy
Divisions: Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Stephen Lowry
Date Deposited: 08 Dec 2015 22:17 UTC
Last Modified: 29 May 2019 16:29 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/52269 (The current URI for this page, for reference purposes)
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