Earth鈥檚 surface may be teeming with trillions of dark matter particles

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When dark matter is captured inside a planet or star, much of it sinks to the middle 鈥� but if it sometimes bounces off regular matter, there may be huge amounts of it lurking just beneath the surface

By Leah Crane

27 September 2022

In November 2019, researchers were astonished when they viewed its image captured by the Hubble Space Telescope. Dark matter is an invisible substance that astronomers believe plays an important role in the formation of galaxies and is thought to comprise 85 percent of the universe?s mass. This discovery not only challenges the ideas of how galaxies form, but also provides evidence that dark matter is real. It shows that dark matter is not always coupled with regular matter in galaxies and that it has its own separate existence. In addition to lacking dark matter, galaxy NGC 1052-DF2 is an anomaly because you can see straight through it. This is called an ultra-diffuse galaxy because it has an extremely low density. As a result of these findings, a team of researchers are hunting for more dark-matter deficient galaxies to better understand the nature of dark matter and the formation of galaxies. — Dark matter could be closer to the surface of stars and planets than we thought
NASA, ESA, and P. van Dokkum

Dark matter can be trapped inside massive objects, and much of it may be closer to the surface of stars and planets than we realised. On Earth, there may be more than 10 trillion dark matter particles in each cubic centimetre of the planet鈥檚 crust.

Dark matter is a hypothetical form of matter that isn鈥檛 visible because it doesn鈥檛 seem to interact with light at all. However, it does interact with regular, or baryonic, matter via gravity, and it is possible that particles of dark matter may occasionally smash into particles of baryonic matter.

at Stanford University in California and at the University of Liverpool in the UK calculated how these collisions would affect the distribution of dark matter inside celestial bodies. Our galaxy and most others are听embedded in huge clouds of dark matter, so there is most likely a constant stream of these particles entering every planet and star in the galaxy.

The story of the Higgs boson

Leane and Smirnov found that this dark matter doesn鈥檛 simply sink to the centres of planets and stars as some past research has assumed. 鈥淚f you鈥檙e a dark matter particle, you have gravity pulling you towards the centre of the star or the planet, but as you head down you鈥檙e bouncing off of all the matter on the way to the core,鈥� says Leane. 鈥淚t turns out that even if you give the dark matter as much time as it likes, some of it still ends up near the surface because of all this bouncing.鈥�

They calculated that in the sun, this would result in 100 trillion particles of dark matter in each cubic centimetre of the sun鈥檚 surface, or maybe even more, depending on how strongly dark matter interacts with regular matter.

While current dark matter detectors aren鈥檛 built to search for this trapped dark matter 鈥� it is expected to move slower than dark matter hurtling in from space, so it would carry less energy and be harder to detect 鈥� a high concentration near the surface could help future experiments. 鈥淚f there鈥檚 a bunch of dark matter just sitting at the surface of the Earth, that could make it easier to detect,鈥� says Leane.

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Topics: Dark matter

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