A&A 466, 749-753 (2007)
DOI: 10.1051/0004-6361:20066849

A dynamical and observational study of an unstable TNO: 59358 (1999CL₁₅₈)

A. Alvarez-Candal¹, D. Jones², D. Lazzaro¹, I. P. Williams², and M. Melita<sup>3

1</sup>  Observatório Nacional/MCT. Rua Gal. José Cristino 77, Rio de Janeiro 20921-400, RJ, Brazil
    e-mail: alvaro.alvarez@obspm.fr
²  Astronomy Unit, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
³  Instituto de Astronomía y Física del Espacio/CONICET. CC 67 - Suc 28, C1428ZAA, Ciudad Autónoma de Bs. As., Argentina

(Received 30 November 2006 / Accepted 7 February 2007)

Abstract
Context. The physical surface properties of a trans-Neptunian Object is believed to be mainly produced as a result of interplay between irradiation from different kinds of cosmic rays and collisions. Objects recently resurfaced by collisions are likely to have very different physical properties from those of the bulk population. In particular, pristine ices from the interior are expected to be present on the surface. A possible way to identify a trans-Neptunian object that has suffered a major collision is by investigating the lifetime of the orbit near its present location. If the lifetime is very short, a physical encounter is a possible way by which the TNO has evolved into such a short lived orbit.
Aims.The goal of this investigation is to search for tracers of a young surface on objects with very short orbital lifetimes in the trans-Neptunian Belt. We are looking for any evidence that indicates that they reached their current unstable orbits through collisions. In particular, we have studied the case of 59358 (1999CL₁₅₈), a trans-Neptunian object that currently has the most chaotic orbit in the Classical Belt.
Methods.By numerically integration its orbit, we estimate that 59358 (1999CL₁₅₈) has resided near its location for about 10 Myr. We have also obtained a near-infrared spectrum of 59358 (1999CL₁₅₈) in the region between 1.43-1.96 microns using the near infrared imager and spectrograph, NIRI, at Gemini North 8-m telescope. These NIR observations are of the faintest and smallest TNO so far observed.
Results.We present the results of the search of ice-bands, such as CH₄ and H₂O, having found evidence of the presence of the first mentioned molecule.
Conclusions.The detection of methane implies that it must be an abundant component of this object. Methane is also evidence of a young surface, therefore we conclude that it is likely that 59358 (1999CL₁₅₈) has experienced a recent collision or collisions.

Key words: Kuiper Belt -- techniques: spectroscopic

© ESO 2007

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