Astron. Astrophys. 329, 1145-1151 (1998)

4. Conclusions

We have presented and discussed dynamical and spectral properties of 3 dark asteroidal objects. The dynamical behaviors of these bodies are considerably different. (6042) 1990 WW₂ has a high-inclination orbit and, during the period in which has been analyzed (821.4 years), it does not show any large variations in semi-major axis, aphelion and perihelion distance.

(6144) 1994 EQ₃ shows a very irregular orbital evolution: it undergoes several close encounters with Jupiter and its semi-major axis changes very rapidly. According to its dynamical behavior, this object could be an Edgeworth-Kuiper Belt comet or a fragment of a recent family-forming event in the Trojan cloud. This last possibility is suggested by the fact that 3 clones of its actual orbit, integrated backward in time, are trapped in Jupiter's horseshoe orbits for more than years.

1995 QY₂ is a Mars crosser and librates about the 15/7 mean-motion resonance with Jupiter. However, the resonance trapping is not stable and small variations of its orbital parameters can generate different orbital evolutions after the resonance escape: 9 over 15 clones of the original orbit jump on several other resonances with Jupiter and some of them become Earth crossing before the end of the integration. 6 clones end up in Jupiter-crossing orbits on a timescale of the order of yr and, from a dynamical point of view, they become comets.

These dynamical differences do not correspond to strong spectral differences: all spectra show the typical trend of carbon-rich, low albedo, "primitive" objects and are compatible with those of outer-belt asteroids. Results seem to confirm the hypothesis that some low-albedo objects could have cometary origin. In particular, the relatively high redness of (6144) 1994 EQ₃ (similar to that of three comet nuclei), coupled with its peculiar dynamical characteristics, support the hypothesis about a possible cometary origin of dark asteroids, which could be exhausted comet nuclei.

© European Southern Observatory (ESO) 1998

Online publication: December 16, 1997
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