On the Existence of a Primordial Cometary Belt between Uranus and Neptune

BRUNINI, A. MELITA, M. D.

ICARUS

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 1998 vol. 135 p. 408 - 412

0019-1035

The existence of stable orbits in the interplanetary region between Uranus and Neptune over the lifetime of the Solar System has been reported by Holman (1997, Nature387, 785-788). A long-term integration of test particles in that zone resulted in a number of surviving bodies with semimajor axis roughly between 24 and 27 AU, and eccentricities and inclinations smaller than 10 -2and 1°, respectively. According to up-to-date surveys, the total mass of this putative belt has been estimated as ≤ 10 -3M⊕and it would be composed of objects with radius smaller than 50 km. In this work we assess the plausibility of the existence of a real population of objects in such a belt. Time-reversal arguments rule out the possibility of capture in such long-term stable orbits, for example, of objects escaped from the Kuiper belt. So if a real population exists nowadays, it should have undergone the conditions of planetesimal accretion in the region. Hence, we have studied the orbital evolution of test particles under different kinds of plausible primordial scenarios. The conditions considered were mutual collisions and gravitational encounters, planetary migration and the presence of an adjacent Pluto-sized object. Under none of these conditions have we obtained a surviving substantial population on the reported belt region, from which it is concluded that, at present time, it would be very unlikely to find a subtantial number of primordial objects in those long-term stable orbits.