Dark matter 'hairs' around Earth?

Simulations of the behaviour of dark matter have hypothesized dark matter 'hairs' protruding from planetary bodies that could potentially be studied to reveal more about the mysterious substance.

An illustration showing Earth surrounded by the theoretical dark mater 'hairs'. The image, however, is not to scale. SImulations show the roots could extend 1 million kilometres from Earth, while Earth's radius is only about 6,400 kilometres.
Credit: NASA/JPL-Caltech

When streams of dark matter pass through a planet, they form dense ‘hairs’ that could be potentially studied to enable scientists to learn more about the invisible substance.

These findings are a result of a new study at NASA’s Jet Propulsion Laboratory.

Dark matter is invisible, hypothetical and makes up about 27 per cent of all matter and energy in the Universe. While it has never been fully detected, its existence is inferred from its gravitational effect on the visible matter in the Universe.

Calculations in the 1990s and recent simulations show how dark matter forms streams of particles that orbit galaxies.

“A stream can be much larger than the Solar System itself, and there are many different streams crisscrossing our galactic neighborhood,” says study author Gary Prézeau.

Prézeau’s calculations show that, if one of these streams of dark matter passed through a planet, that planet’s gravity would focus the stream into a narrow, dense ‘hair’.

These ‘hairs’ would then protrude from the planet’s surface: there could even be dark matter hairs protruding from Earth. They have both a root, where the concentration of particles is densest, and tips, where the hair ends. When the particles of a dark matter stream pass through Earth’s core, they focus at the root of a hair, which should be around 1 million kilometres away from the surface.

“If we could pinpoint the location of the root of these hairs, we could potentially send a probe there and get a bonanza of data about dark matter,” Prézeau says.

“Dark matter has eluded all attempts at direct detection for over 30 years. The roots of dark matter hairs would be an attractive place to look, given how dense they are thought to be,” adds Charles Lawrence, chief scientist for JPL’s astronomy, physics and technology directorate.

These hairs could also be used to detect changes in the density of our own planet, from the inner core to the outer core, as the hairs would display ‘kinks’ corresponding to these different layers. Such information could theoretically be used to map the inner structures of any planetary body, including the oceans of icy moons.

Further studies will now be undertaken to confirm Prézeau’s findings.


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