Observing the variation of asteroid thermal inertia with heliocentric distance

Rozitis, B.; Green, S. F.; MacLennan, E. and Emery, J. P. (2018). Observing the variation of asteroid thermal inertia with heliocentric distance. Monthly Notices of the Royal Astronomical Society, 477(2) pp. 1782–1802.

DOI: https://doi.org/10.1093/mnras/sty640

Abstract

Thermal inertia is a useful property to characterise a planetary surface since it can be used as a qualitative measure of the regolith grain size. It is expected to vary with heliocentric distance because of its dependence on temperature. However, no previous investigation has conclusively observed a change in thermal inertia for any given planetary body. We have addressed this by using NEOWISE data and the Advanced Thermophysical Model to study the thermophysical properties of the near-Earth asteroids (1036) Ganymed, (1580) Betulia, and (276049) 2002 CE26 as they moved around their highly eccentric orbits. We confirm that the thermal inertia values of Ganymed and 2002 CE26 do vary with heliocentric distance, although the degree of variation observed depends on the spectral emissivity assumed in the thermophysical modelling. We also confirm that the thermal inertia of Betulia did not change for three different observations obtained at the same heliocentric distance. Depending on the spectral emissivity, the variations for Ganymed and 2002 CE26 are potentially more extreme than that implied by theoretical models of heat transfer within asteroidal regoliths, which might be explained by asteroids having thermal properties that also vary with depth. Accounting for this variation reduces a previously observed trend of decreasing asteroid thermal inertia with increasing size, and suggests that the surfaces of small and large asteroids could be much more similar than previously thought. Furthermore, this variation can affect Yarkovsky orbital drift predictions by a few tens of per cent.

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About

  • Item ORO ID
  • 54142
  • Item Type
  • Journal Item
  • ISSN
  • 1365-2966
  • Project Funding Details
  • Funded Project NameProject IDFunding Body
    Probing solar system process using extreme asteroidsNot SetRoyal Astronomical Society (RAS)
    Consolidated Grant - Solar Studies and Planetary Studies (SS & PL 2016)ST/P000657/1STFC (Science & Technology Facilities Council)
    Astronomy and Planetary Sciences at the Open UniversityST/L000776/1STFC (Science & Technology Facilities Council)
  • Keywords
  • radiation mechanisms: thermal, methods: numerical, minor planets, asteroids: individual: (1036) Ganymed, (1580) Betulia, (276049) 2002 CE26, celestial mechanics
  • Academic Unit or School
  • Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
    Faculty of Science, Technology, Engineering and Mathematics (STEM)
  • Research Group
  • Space
  • Copyright Holders
  • © 2018 The Authors
  • Depositing User
  • Benjamin Rozitis

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