Is Earth Surrounded by “Hairy” Dark Matter?

November 30, 2015 | Joanne Kennell

Hairs of dark matter stretching away from Earth's surface
Photo credit: NASA/JPL-Caltech

The universe might be a lot hairier than we thought.

A radical new idea by Gary Prézeau of NASA’s Jet Propulsion Laboratory in Pasadena, California, proposes the existence of long filaments or “hairs” of dark matter stretching away from Earth’s surface.

If the hypothesis is confirmed, scientists may finally be able to detect this elusive dark matter for the first time.  It would also be a little ironic — something thought to be only detectable in deep space is actually surrounding the entire planet and at a fairly short distance.

Dark matter is an invisible substance that makes up 27 percent of all matter and energy in the universe, and normal matter — everything that has ever been observed by humans — makes up only five percent.  The rest is made up of dark energy, something that scientists know very little about, other than that it is a strange phenomena associated with the accelerated expansion of our universe.

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Scientists know dark matter exists because they are able to measure its gravitational pull on other objects in the universe, but it has never been detected because it does not interact with light.

Previous research suggested that dark matter forms as streams of particles that move at the same velocity and orbit galaxies.  "A stream can be much larger than the solar system itself, and there are many different streams crisscrossing our galactic neighborhood," Prézeau said.

The question that came to mind next for Prézeau was what would happen when these streams approach a planet like Earth?  He used computer simulations to find out.

As it turns out, Earth is not really an obstacle for dark matter, but Earth’s gravity causes the streams of dark matter particles to bend into a narrow filament as they travel through the planet.  Not only that, the different layers within Earth’s interior would cause the hairs to bend and kink because of the varying densities.

As the “hairs” enter and emerge from Earth, they have both “roots” — the densest concentration of particles — and “tips”, where the hair ends.  According to Prézeau’s simulations, the roots will form about 600,000 miles from Earth, twice as far as the moon, and will have a density one billion times more than the rest of the stream.  Hard to imagine, but maybe large enough to measure.

Much more research is required to confirm Prézeau’s theory, however if confirmed, he has given the world an approximate location of where dark matter can be detected.

"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 said.

His study was published on November 25 in Astrophysical Journal.

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