By Michelle Starr
When we peer out into intergalactic space, evidence for dark matter is everywhere. It’s in the rotation of galaxies, which cannot be accounted for by observable matter alone. It’s in the way galaxies cluster together, and the path of light as it travels through the Universe. We can’t see dark matter directly, but the effects it has on other objects has allowed us to map it pretty comprehensively on large scales.
Closer to home, however – actually within the Milky Way galaxy – and on sub-galactic scales, the effects of dark matter are much smaller, and therefore a lot more difficult to map. But a new technique could finally tease out where the Milky Way’s dark matter is hiding, by looking for a telltale warp in the light from stars when dark matter passes in front of them.
Dark matter is one of the most perplexing phenomena in the cosmos. We can’t detect it directly, so we don’t know what it is, but we do know that the amount of gravity in the Universe can’t be accounted for by the normal observable matter – what we call baryonic matter – alone.
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