Probing Oort Cloud and local ISM properties via dust produced in cometary collisions

The Oort Cloud remains one of the most poorly explored regions of the Solar System. We propose that its properties can be constrained by detecting and studying from space a population of dust grains produced in collisions of comets in the outer Solar System. We explore the dynamics of micron-size grains outside the heliosphere (beyond ~250 AU), which are affected predominantly by the magnetic field of the interstellar medium (ISM) flow past the Sun. We derive analytic models for the production and motion of small particles as a function of their birth location in the Cloud and calculate particle flux and velocity distribution in the inner Solar System. These models are verified by direct numerical simulations. We show that grains originating in the Oort Cloud have a unique distribution of arrival directions (mainly perpendicular to both the ISM wind velocity and the ISM magnetic field), which should easily distinguish them from both interplanetary and interstellar dust populations. We also demonstrate that the distribution of particle arrival velocities is uniquely related to the spatial distribution of the dust production inside the Cloud. The latter is, in turn, determined both by the mass distribution in the Cloud and the physical properties of comets. Cometary collisions within the Oort Cloud are expected to produce a flux of micron-size grains in the inner Solar System of up to several m^{-2} yr^{-1}. The next-generation dust detectors may be sensitive enough to detect and constrain this dust population, which will illuminate us about the Oort Cloud’s properties. We also show that the recently-detected mysterious population of large (micron-size) unbound particles, which seems to arrive with the ISM flow is unlikely to be of a cometary origin.

Read this paper on arXiv…

Date added: Fri, 11 Oct 13