Hills cloud

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The Hills cloud is a hypothetical inner region of the Oort cloud with an outer boundary of 2-3×10⁴ AU, and a less well defined inner boundary at 50 to 3000 AU, proposed in 1981 by J. G. Hill. It was suggested as a source that delivers comets to a relatively tenuous outer Oort halo, resupplying it as the outer halo is depleted by closely passing stars or gigantic molecular complexes and by galactic tidal effects. It is predicted that it has one to two orders of magnitude more cometary nuclei than the outer halo.

[edit] References

• Heisler, Julia, Scott Tremaine (1986). "The influence of the galactic tidal field on the Oort comet cloud". Icarus 65: 13.
• Hills, Jack G. (November 1981). "Comet showers and the steady-state infall of comets from the Oort cloud". Astronomical Journal 86: 1730-1740. DOI:10.1086/113058.
• Marochnik, Leonid S., Mukhin, Lev M., Zagdeev, Roald S. (1991). “The Oort Cloud”, Planetary Sciences: American and Soviet Research/Proceedings from the U.S.-U.S.S.R. Workshop on Planetary Sciences, 251.