Author:PrézeauAbstract:It is shown that compact bodies project out strands of concentrated dark matter filaments, henceforth simply called hairs. These hairs are a consequence of the fine-grained stream structure of dark matter halos, and as such constitute a new physical prediction of ΛCDM. Using both an analytical model of planetary density and numerical simulations utilizing the Fast Accurate Integrand Renormalization algorithm (a fast geodesics calculator described below) with realistic planetary density inputs, dark matter streams moving through a compact body are shown to produce hugely magnified dark matter densities along the stream velocity axis passing through the center of the body. Typical hair density enhancements are 107 for Earth and 108 for Jupiter. The largest enhancements occur for particles streaming through the core of the body that are mostly focused at a single point called the root of the hair. For the Earth, the root is located at about 106 km from the planetary center with a density enhancement of around 109 while for a gas giant like Jupiter, the root is located at around 105 km with an enhancement of around 1011. Beyond the root, the hair density precisely reflects the density layers of the body, providing a direct probe of planetary interiors.