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On a collision course: A flood of dark matter is blowing into our solar system – and at high speed, as astronomers have discovered. At about 500 kilometers per second, this so-called "S1 current" moves twice as fast in the Milky Way as our sun. It does not hurt us, but it could facilitate the future search for particles of this exotic form of matter in this "storm" of dark matter.
The Milky Way is traversed by many star streams, one of which drives dark matter through our solar system.
© NASA / JPL-Caltech / R. Hurt (SSC / Caltech) 
There is four times more dark matter than normal matter in the cosmos – yet we know almost nothing about it. It only seems clear that dark matter occurs almost everywhere in the universe – in our galaxy of the Milky Way, as well as in dwarf galaxies, powerful streams and perhaps even fine "hairs" near the Earth. Their gravitational influence links galaxies and also shapes the movement of star clusters around our cosmic neighborhood.
Sternenstrom on a collision course
Such flows of dark matter also exist in our Milky Way. They were created when neighboring dwarf galaxies were torn apart by the gravitational influence of our galaxy. What remained were streams of gas, stars and dark matter. "There are tons of these currents in our galaxy, some of them are so big that you can see them in the sky," says Ciaran O. Hare of the University of Zaragoza.
But one of these flows is particularly exciting. Because its path crosses our sun, astronomers did not discover last year that the satellite data Gaia. So, our solar system is in the middle of this huge stream of 30,000 stars and much more dark matter. The sun and this so-called stream S1 move on the same elliptical orbit as by the milky way.
Current S1, star motions and orbit our sun.
© C. O & # 39; Hare, NASA / Jon Lomberg
"Hurricane" by Dark Matter
The interesting thing about this: the S1 current is exceptionally fast, as determined by O & # 39; Hare and his colleagues. According to his calculations, dark matter crosses the Milky Way at about 500 kilometers per second, twice as fast as our sun. Because it runs around the center of the Milky Way at about 240 kilometers an hour.
But that means our solar system is constantly subjected to an invisible and not directly detectable dark matter storm. In a comment from the American Physical Society, there is even talk of a "hurricane of dark matter". But you do not have to worry about it because we do not notice anything about this storm of dark matter and it does not harm us either.
Possibility of detecting axions
The discovery of the Dark Matter Stormband sheds new light on our chance to finally prove the enigmatic particles of dark matter. Thanks to the fast current S1, dark matter particles should also be blown into our solar system and down to Earth. O & # 39; Hare and his team have calculated if and with what detectors this might be possible.
As a result, current detectors looking for low interaction solid particles (WIMP) as dark matter particles are unlikely to succeed. This is different with detectors looking for axions – also purely hypothetical particles, which are significantly lighter than WIMPs. According to astronomers, the sensitivity of these detectors is in a range sufficient to detect the axions of the current S1 – if the axions actually exist. (Physical Review D, 2018, doi: 10.1103 / PhysRevD.98.103006)
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