Peculiar Betulia Revisited: A Near-Earth Asteroid with a Bare-Rock Surface?
Harris, Alan and Mueller, Michael and Delbo, Marco and Bus, Schelte (2005) Peculiar Betulia Revisited: A Near-Earth Asteroid with a Bare-Rock Surface? In: Bulletin of the American Astronomical Society, 37 (3), p. 628. American Astronomical Society. 37th DPS-Meeting of the American Astronomical Society, 2005-09-04 - 2005-09-09, Cambridge (UK).
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The small C-type asteroid (1580) Betulia is an unusual near-Earth object (NEO) with a lightcurve that changes dramatically with changing solar phase angle, presumably due to a highly irregular shape and/or unusual topographic features. Earlier thermal-infrared observations indicated a surface of high thermal inertia, which is consistent with a lack of thermally insulating regolith. Absence of regolith might be expected in the case of small NEOs with weak gravities, which may be unable to retain collisional debris. However, recent infrared observations of other asteroids of comparable size indicate that regolith is normally present. Knowledge of the thermal properties of NEOs is crucial for meaningful calculations of the Yarkovsky effect, which is invoked to explain the delivery of collisional fragments from the main belt into near-Earth orbits, and apparently has a significant influence on the orbital evolution of potentially hazardous NEOs. We observed Betulia in June 2002 with the 3-m NASA Infrared Telescope Facility. Our database is sufficiently broad to allow the use of more sophisticated thermal models than were available for earlier radiometric observations. It is important to bear the unusual nature of Betulia in mind when interpreting observational data. Fits to our data obtained with a new thermophysical model imply an effective diameter of 4.57±0.46 km and an albedo of 0.077±0.015, and indicate a moderate surface thermal inertia of around 180 Jm<sup>-2</sup>s<sup>-0.5</sup>K<sup>-1</sup>. It is difficult to reconcile our results with those of earlier work, which indicate a larger diameter for Betulia and a high-thermal-inertia surface of bare rock. While the thermal inertias of NEOs appear to be significantly higher than those of large main-belt asteroids, to our knowledge no convincing evidence has yet been found for very high-thermal-inertia “bare-rock” surfaces amongst NEOs: further observations are required to probe smaller objects.
|Document Type:||Conference or Workshop Item (Speech)|
|Title:||Peculiar Betulia Revisited: A Near-Earth Asteroid with a Bare-Rock Surface?|
|Journal or Publication Title:||Bulletin of the American Astronomical Society|
|In ISI Web of Science:||No|
|Page Range:||p. 628|
|Publisher:||American Astronomical Society|
|Keywords:||Asteroids, near-Earth asteroids, infrared observations, thermal models|
|Event Title:||37th DPS-Meeting of the American Astronomical Society|
|Event Location:||Cambridge (UK)|
|Event Type:||international Conference|
|Event Dates:||2005-09-04 - 2005-09-09|
|Organizer:||AAS Division for Planetary Sciences|
|HGF - Research field:||Aeronautics, Space and Transport|
|HGF - Program:||Space|
|HGF - Program Themes:||W EW - Erforschung des Weltraums|
|DLR - Research area:||Space|
|DLR - Program:||W EW - Erforschung des Weltraums|
|DLR - Research theme (Project):||W - Vorhaben Asteroiden und Kometen (old)|
|Institutes and Institutions:||Institute of Planetary Research > Asteroids and Comets|
|Deposited By:||Prof. Alan Harris|
|Deposited On:||11 Dec 2005|
|Last Modified:||27 Apr 2009 04:45|
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