\n<\/p>\n
It\u2019s been a very busy dark matter hunting season so far. Already, one research team says they\u2019ve found evidence for self-interacting dark matter in an enormous galaxy cluster. And another team says dark matter might be causing a glow on Jupiter\u2019s dark side.<\/p>\n
Now three more research groups say they\u2019re extending the hunt for dark matter to new extremes. The first team is looking 250,000 light-years away at the Draco dwarf galaxy. A second team thinks we can detect dark matter just over our heads in our planet\u2019s atmosphere. And a third says the signature of dark matter is imprinted on the Earth itself.<\/p>\n
Results of a peer-reviewed, 18-year-long stellar survey showing dark matter density in the Draco galaxy appeared in the Astrophysics Journal<\/em> in July 2024. The scheme for detecting dark matter in Earth\u2019s ionosphere appeared as a preprint paper in Cornell University\u2019s open-source archive \u2013 arXiv.org \u2013 in May 2024. And the paper proposing a search for dark matter signals in rocks published in July 2024 in the journal Symmetry<\/em>.<\/p>\n We know almost nothing about dark matter. We don\u2019t know what it\u2019s made from. Dark matter can\u2019t be felt or heard \u2026 at least not yet. And, of course, it\u2019s so dark we can\u2019t see it.<\/p>\n But \u2013 thanks to the work of astronomers like Vera Rubin \u2013 we do know that its gravitational effect holds galaxies together. If it weren\u2019t for dark matter, there wouldn\u2019t be enough mass in galaxies to keep stars from flinging into space. That means whatever it is, there\u2019s a whole lot of it. Dark matter makes up roughly 27% of the mass of everything there is.<\/p>\n Dark energy accounts for almost everything else. It makes up 68% or so of the cosmos. That leaves about 5% of the universe\u2019s mass in the form of regular matter like us.<\/p>\n So, dark matter is a sort of cosmic glue holding things together. But we only have tantalizing clues about what it is.<\/p>\n So the only handle we have on dark matter is its pull on everything else. While the stuff doesn\u2019t appear to interact with electromagnetic radiation \u2013 like light, gamma radiation and X-rays \u2013 it does warp the fabric of spacetime. In other words, it has gravity.<\/p>\n 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 at the center of galaxies, in areas known as density cusps. However, some observations suggested dark matter might be evenly dispersed in a galaxy.<\/p>\n So researchers with NASA, ESA and the Space Telescope Science Institute (STScI) spent a decade searching through 18 years\u2019 worth of archival data from the Hubble Space Telescope. With it, they constructed highly detailed models of stellar motions in the Draco dwarf galaxy. STScI\u2019s Eduardo Vitral, the lead author of the study, described what the team found in a NASA press release:<\/p>\n Our models tend to agree more with a cusp-like structure, which aligns with cosmological models. While we cannot definitively say all galaxies contain a cusp-like dark matter distribution, it\u2019s exciting to have such well measured data that surpasses anything we\u2019ve had before.<\/p>\n<\/blockquote>\n Scientists are already applying the same method to the Sculptor and Ursa Minor dwarf galaxies. The insight into dark matter this method provides will become more detailed as new instruments like the Nancy Grace Roman Space Telescope come online.<\/p>\n Meanwhile, another trio of physicists said the model they created of Earth\u2019s ionosphere shows that dark matter can interact with plasma. And if the plasma has the right frequency \u2013 the same as the dark matter \u2013 then it produces low-frequency radio emissions.<\/p>\n If that hypothesis is right, then we just need to listen in, said the paper\u2019s authors:<\/p>\n An electrically small dipole antenna targeting the generated radio waves can be orders of magnitude more sensitive to dark photon and axion-like particle dark matter in the relevant mass range. The present study opens up a promising way of testing a hitherto unexplored parameter space which could be further improved with a dedicated instrument.<\/p>\n<\/blockquote>\n The catch is dark matter must exist as axions for this to work. These are theoretical elementary particles that scientists first proposed in the 1970s. They, too, have never been definitively detected.<\/p>\n Another paper appearing on arXiv.org in May 2024 wonders if theoretical dark matter particles are behind strange, yet-to-be-explained events on Earth. Author Ariel Zhitnitsky, a physicist at the University of British Columbia, said the enigmas could be explained by axion quark nuggets striking our planet:<\/p>\n It has been recently argued that there are a number of mysterious observations which are very hard to explain by conventional physics. The mysterious anomalies include (but are not limited to) such unexpected correlations as temperature variation in the stratosphere, the total electron content of the Earth\u2019s atmosphere, the earthquake activity from one hand, and positions of the planets from another hand.<\/p>\n<\/blockquote>\n Zhitnitsky\u2019s comment refers to work by other theorists. Unfortunately, the brief available online provides no details. However, the physicist said these and other puzzles may be explained by dark matter striking Earth:<\/p>\n It has been hypothesized that the corresponding mysterious correlations are a result of the \u2018streaming invisible matter\u2019 which suddenly becomes very strongly interacting material when entering the Earth\u2019s atmosphere. We propose that some of these (and many other) mysteries might be result of rare (but energetic) events when the so-called axion quark nuggets (AQN) hit the Earth.<\/p>\n<\/blockquote>\n Theoretical particles come in matched pairs of opposites. In this case, it\u2019s the aptly named \u201caxion antiquark nugget\u201d (AQ\u00afN). If these nuggets exist, they\u2019ll have very little mass compared to their size. That means we\u2019d need a huge detector, something about, say, the size of Earth.<\/p>\n A paper published just this month (July 2024) proposes a way to look for evidence of dark matter interactions in the rocks below our feet:<\/p>\n This paper presents a new idea for the direct detection of the AQ\u00afNs using minerals as natural rock deposits acting as paleo-detectors, where the latent signals of luminescence produced by interactions of AQ\u00afNs are registered and can be identified as an increased and symmetrical deposited dose.<\/p>\n<\/blockquote>\n In other words, the light produced by AQN\/AQ\u00afN interactions ongoing since the universe began should leave a trace on Earth\u2019s geology. The signal should be detectable, according to the theory, in various minerals from natural deposits. Now, like dark matter, they just have to find it.<\/p>\n Bottom line: Recent research suggests evidence for dark matter is \u2013 or might be found \u2013 in extreme locations. Researchers are looking in distant galaxies and here on Earth.<\/p>\n Source: Resonant Conversion of Wave Dark Matter in the Ionosphere<\/p>\n Source: HSTPROMO Internal Proper-motion Kinematics of Dwarf Spheroidal Galaxies. I. Velocity Anisotropy and Dark Matter Cusp Slope of Draco<\/p>\n Via NASA<\/p>\n Read more: Do dark matter collisions on Jupiter glow in the infrared?<\/p>\n Read more: Did colliding dark matter shape the El Gordo galaxy cluster?<\/p>\n <\/div>\nWhat the heck is dark matter?<\/h3>\n
Making a motion map of a pint-sized galaxy\u2019s stars<\/h3>\n
\n
Tuning in dark matter radio signals<\/h3>\n
\n
Axion quark nuggets<\/h3>\n
\n
\n
Evidence right under our feet?<\/h3>\n
\n