The solar system is hairy? Thanks to dark matter, this might actually be the case.
This week a study will publish in the Astrophysical Journal by Gary Prézeau of NASA’s Jet Propulsion Laboratory in Pasadena, California. Prézeau proposes the existence of long, hair-like structures of dark matter that form around the Earth.
While normal (baryonic) matter makes up everything we can touch and see, it is only makes up about 15 percent of the matter in the universe. The rest is understood to be dark matter, which is an invisible, mysterious substance that accounts for 85 percent of what holds galaxies together and 85 percent of the attraction that galaxies have toward each other.
While dark matter is understood to gravitationally interact with normal matter, dark matter and normal matter for the most part pass right through each other. The leading theories about dark matter also point to it being “cold,” meaning it moves through the universe at speeds much lower than the speed of light.
While the last 30 years have been full of efforts to directly observe dark matter, be they through underground detectors or space telescopes, so far it hasn’t been detected. Computations, however, are giving insights into how dark matter may be structured within our own solar system.
From simulations performed in the 1990s and 2000s, it’s been suggested that dark matter forms “fine-grained streams” of particles that crisscross all over our galaxy and its neighbors. “Fine” is a relative term because these streams can be wider than our entire solar system. Said Prézeau in a NASA press release, “When gravity interacts with the cold dark matter gas during galaxy formation, all particles within a stream continue traveling at the same velocity.”
Prézeau’s new simulations investigate what happens when one of these streams interacts with planets like Earth and Jupiter. He found that when a dark-matter stream goes through a planet, the dark matter becomes focused and bent into long, hair-like structures that point directly at the planet. Even more strangely, dark matter concentrates at either end of these hairs: the roots and tips.
The roots of these hairs are understood to be about twice as far from Earth as the moon and the tips are understood to be about twice that distance. The hope is that more research can pinpoint the location of one of these “hair roots” so a probe could be sent there and perhaps collect data that we’ve been unable to collect with the detectors here on Earth.
From the simulations, it’s also predicted that variations of Earth’s density (such as the core, mantle and crust) cause variations within the dark-matter hairs. If probes are able to detect the dark matter in these hairs with enough sensitivity, dark-matter measurements could in turn be used to learn about other planets and moons. In the future it may be possible to investigate the depths of alien worlds by looking at the hairs of dark matter that surround each one.