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

Rozitis, B. and Duddy, S.R. and Green, S.F. and Lowry, S.C. (2013) A thermophysical analysis of the (1862) Apollo Yarkovsky and YORP effects. Astronomy and Astrophysics, 555 . (A20) 1-12. ISSN 0004-6361. E-ISSN 1432-0746. (doi:https://doi.org/10.1051/0004-6361/201321659) (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)

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Official URL
http://dx.doi.org/10.1051/0004-6361/201321659

Abstract

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 140-100 +140140-100+140 J m-2 K -1 s-1/2, a highly rough surface, and a bulk density of 2850-680 +480+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 -0.5 +0.3 +0.3-0.5 degrees per 105 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. © 2013 ESO.

Item Type: Article
Additional information: Unmapped bibliographic data: C7 - A20 [EPrints field already has value set] LA - English [Field not mapped to EPrints] J2 - Astron. Astrophys. [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 - Centre for Astrophysics and Planetary Science, School of Physical Sciences (SEPnet), University of Kent, Canterbury, CT2 7NH, United Kingdom [Field not mapped to EPrints] DB - Scopus [Field not mapped to EPrints]
Uncontrolled keywords: Celestial mechanics, Infrared: planetary systems, Methods: data analysis, Minor planets, asteroids: individual: (1862) Apollo, Radiation mechanisms: thermal, Celestial mechanics, Infrared: planetary systems, Methods:data analysis, Minor planets , asteroids, Radiation mechanisms: thermal, Astrophysics, Forecasting, Long Term Evolution (LTE), Surface measurement, Thermodynamic properties, 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 22:09 UTC
Last Modified: 21 Dec 2015 16:21 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/52276 (The current URI for this page, for reference purposes)
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