Observing the variation of asteroid thermal inertia with heliocentric distance

B. Rozitis, S. F. Green, E. MacLennan, J. P. Emery

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Thermal inertia is a useful property to characterize 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 (276 049) 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.

Original languageEnglish (US)
Pages (from-to)1782-1802
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Volume477
Issue number2
DOIs
StatePublished - Jun 21 2018
Externally publishedYes

Keywords

  • (1580) Betulia
  • (276 049) 2002 CE26
  • Asteroids: Individual: (1036) Ganymed
  • Celestial mechanics
  • Methods: Numerical
  • Minor planets
  • Radiation mechanisms: Thermal

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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