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Astron. Astrophys. 329, 785-791 (1998)

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5. Summary

We estimated the dust production rate by impacts of interstellar dust grains on EKOs. If EKOs have hard icy surfaces, and there are 1013 of these with radius [FORMULA] 0.1km, we find that the total dust production rate over the entire Edgeworth-Kuiper Belt is between [FORMULA] g s-1 and [FORMULA] g s-1, depending on the adopted minimum ejection velocity of 10 cm s [FORMULA] 103 cm s-1, and on the size distribution of the EKOs. On the other hand, if the surfaces of EKOs are covered by a layer of icy particles, the total dust production rate is [FORMULA] g s [FORMULA] g s-1. These results suggest that, in addition to mutual collisions of EKOs, impacts by interstellar dust are a significant source of interplanetary dust grains with radii less than about 10 [FORMULA], and which exist at large distances from the sun.

After leaving the Edgeworth-Kuiper Belt, the orbits of the dust grains evolve under the complex influences of the gravitational forces of the Sun and the giant planets, as well as solar radiation pressure and Poynting-Robertson drag forces. The mutual collisions of debris particles and the collisions by interstellar dust grains may also play important roles in the evolution of dust grains. Liou et al. (1996) showed that a grain with diameter larger than about 9 [FORMULA] is destroyed by the mutual collisions of debris and by the impact of interstellar dust before reaching the inner Solar System, whereas smaller grains can evolve towards the inner Solar System under Poynting-Robertson drag forces. The results of Liou et al. (1996) show that about 80% of the smaller grains produced in the Edgeworth-Kuiper Belt are ejected from the Solar System by the giant planets, while 20% of the grains enter the inner Solar System under the Poynting-Robertson drag forces. The maximum radius of the grains produced by the impact of interstellar dust is about 10 [FORMULA] as mentioned above. Thus, a fraction of the dust grains produced by the impact of interstellar dust on EKOs may contribute to the population of the interplanetary dust inside the orbit of Jupiter. However, the sublimation of icy particles should be taken into account when estimating the lifetime of the grains at such distances (Mukai 1986). Further investigations are required to understand the contribution of these grains to the interplanetary dust in the inner Solar System.

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© European Southern Observatory (ESO) 1998

Online publication: December 8, 1997