The Cloudy Universe
Abstract
Modelling of Extreme Scattering Events suggests that the Galaxy's dark matter is an undetected population of cold, AU-sized, planetary-mass gas clouds. None of the direct observational constraints on this picture -- thermal/non-thermal emission, extinction and lensing -- are problematic. The theoretical situation is less comfortable, but still satisfactory. Galactic clouds can survive in their current condition for billions of years, but we do not have a firm description for either their origin or their evolution to the present epoch. We hypothesise that the proto-clouds formed during the quark-hadron phase transition, thereby introducing the inhomogeneity necessary for compatibility with light element nucleosynthesis in a purely baryonic universe. We outline the prospects for directly detecting the inferred cloud population. The most promising signatures are cosmic-ray-induced H-alpha emission from clouds in the solar neighbourhood, optical flashes arising from cloud-cloud collisions, ultraviolet extinction, and three varieties of lensing phenomena.
Cite
@article{arxiv.astro-ph/9907260,
title = {The Cloudy Universe},
author = {Mark Walker and Mark Wardle},
journal= {arXiv preprint arXiv:astro-ph/9907260},
year = {2015}
}
Comments
16 pages, LaTeX, no figures, to appear in Pub. Ast. Soc. Aus