Searching for dark matter from Earth to distant galaxies
It's been a very busy day. dark matter hunting season so far. A research team already says it has found evidence of self-interacting dark matter in a huge galaxy cluster. And another team says dark matter could be causing a glow on the dark side of Jupiter.
Now, three other research groups say they are expanding the search for dark matter to new extremes. The first team is looking 250,000 light years far away in the Draco dwarf galaxyA second team believes we can detect dark matter just above our heads, in our planet's atmosphere. And a third says the fingerprint of dark matter is imprinted on Earth itself.
Results of a peer reviewedAn 18-year star survey reveals the density of dark matter in the Draco galaxy appeared in it Journal of Astrophysics in July 2024. The plan to detect dark matter in the Earth's ionosphere appeared as a prepress paper on Cornell University's open source archive – arXiv.org – in May 2024. And the article proposing a search for dark matter signals in rocks published in July 2024 in the magazine Symmetry.
What the hell is dark matter?
We know almost nothing about dark matter. We don't know what it's made of. Dark matter can't be felt or heard… at least not yet. And of course, it's so dark that we can't see it.
But, thanks to the work of astronomers like Vera Rubin – We know that its gravitational effect holds galaxies together. If it weren’t for dark matter, there wouldn’t be enough mass in galaxies to stop stars from being flung into space. That means that whatever it is, there’s a lot of dark matter. Dark matter makes up about 27% of the mass of everything that exists.
Dark energy It accounts for almost everything else. It makes up about 68% of the cosmos. That leaves about 5% of the mass of the universe in the form of regular matter like us.
So dark matter is a kind of cosmic glue that holds things together, but we only have tantalizing clues about what it is.
Creating a motion map of the stars in a small galaxy
So the only control we have over dark matter is its attraction to everything else. Although matter doesn't seem to interact with… electromagnetic radiation – like light, gamma radiation and X-rays – warps the fabric of space-time. In other words, it has gravity.
With that in mind, some very clever people designed computer simulations to show where dark matter should accumulate in galaxies. Their models said it should concentrate in the centre of galaxies, in areas known as density cuspsHowever, some observations suggested that dark matter might be evenly dispersed throughout a galaxy.
So researchers from NASA, ESA and the Space Telescope Science Institute (STScI) spent a decade searching through 18 years of archival data from the Hubble Space Telescope. From it, they built highly detailed models of stellar motions in the Draco dwarf galaxy. Eduardo VitralThe study's lead author described what the team found in a NASA study. Press release:
Our models tend to be more in line with a cusp-like structure, which aligns with cosmological models. While we can't definitively say that all galaxies contain a cusp-like distribution of dark matter, it's exciting to have such well-measured data that surpasses anything we had before.
Scientists are already applying the same method to Sculptor and Little Bear dwarf galaxies. The understanding of dark matter provided by this method will become more detailed as new instruments such as the Nancy Grace Roman Space Telescope go online.
Tuning in to dark matter radio signals
Meanwhile, another trio of physicists said the model they created of Earth's ionosphere shows that dark matter can interact with plasma. And if the plasma has the right frequency (the same as dark matter), then it produces low-frequency radio emissions.
If that hypothesis is correct, then we just need to listen. The authors of the article said:
A small electrically Dipole antenna The orientation of the generated radio waves can be orders of magnitude more sensitive to dark photons and axion-like particle dark matter in the relevant mass range. The present study opens a promising avenue to probe a hitherto unexplored parameter space that could be further improved with a dedicated instrument.
The problem is that dark matter must exist as axions for this to work. These are theoretical elementary particles that scientists first proposed in the 1970s. They, too… They have never been definitively detected.
Axion quark nuggets
Another role The paper, which will appear on arXiv.org in May 2024, asks whether theoretical dark matter particles are behind the strange and still unexplained events on Earth. Author Ariel Zhitnitskyphysicist at the University of British Columbia, said the puzzles could be explained by Axion quark nuggets hitting our planet:
It has recently been argued that there are a number of mysterious observations that are very difficult to explain by conventional physics. The mysterious anomalies include (but are not limited to) unexpected correlations such as the temperature variation in the stratospherethe total electron content of the Earth's atmosphere, seismic activity on the one hand, and the positions of the planets on the other.
Zhitnitsky's comment refers to the work of other theorists. Unfortunately, the summary available online does not provide details. However, the physicist said that these and other puzzles could be explained by the impact of dark matter on Earth:
The corresponding mysterious correlations have been hypothesized to be the result of “invisible matter in motion” that suddenly turns into very strongly interacting material upon entering Earth's atmosphere. We propose that some of these (and many other) mysteries could be the result of rare (but energetic) events when so-called axion quark nuggets (AQNs) impact Earth.
Evidence right under our feet?
Theoretical particles come into matched pairs of oppositesIn this case, it is the aptly named “antiquark axion nugget” (AQ¯N). If such nuggets exist, they would have very little mass compared to their size. That means we would need a huge detector – something like the size of the Earth, for example.
A paper published Just this month (July 2024) a way to search for evidence of dark matter interactions in the rocks beneath our feet is being proposed:
In this paper, a new idea is presented for the direct detection of AQ¯Ns using minerals as natural rock deposits acting as paleodetectors, where latent luminescence signals produced by AQ¯Ns interactions are recorded and can be identified as an increased and symmetrical deposited dose.
In other words, the light produced by AQN/AQ¯N interactions that have occurred since the beginning of the universe should leave a trace in the geology of the Earth. The signal should be detectable, according to theory, in various minerals in natural deposits. Now, as with dark matter, it just needs to be found.
Bottom line: Recent research suggests there is evidence for dark matter (or that it could be found) in extreme places. Researchers are looking in distant galaxies and here on Earth.
Source: Resonant conversion of wave-like dark matter in the ionosphere
Read more: Do dark matter collisions on Jupiter glow in the infrared?
Read more: Did colliding dark matter shape the El Gordo galaxy cluster?
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