Dark Matter Hides in Dwarf Galaxies express
Dark matter is like an invisible glue that holds galaxies together. It emits no light, but if its particles collide, gamma rays can flash. Scientists hunted for such flashes in dwarf galaxies — small stellar clusters with lots of dark matter and almost no ordinary matter. It's like listening for a whisper in a quiet room: fewer distractions make it easier to hear.
The HAWC observatory in Mexico is a huge water tank that catches particles from gamma rays. The team improved their data analysis and expanded their list of dwarf galaxies. But even after all those upgrades, no signal appeared. That means dark matter particles collide even more rarely than we hoped.
The result is new limits on how often dark matter particles collide. For masses from 1 to 10 000 TeV (thousands of times heavier than a proton), the upper limit is $10^{-23}$ cm³/s. That's like two dark matter particles meeting once in a trillion years in a cubic centimeter of space.
Dark matter remains invisible, but the search goes on. Every 'no' narrows the range of possible theories. Maybe next time we'll get luckier.
Original abstract
as written by the authors arXiv:2602.05955
Understanding dark matter's elusive nature is crucial for the framework of particle physics and expanding the Standard Model. This analysis utilizes the High Altitude Water Cherenkov (HAWC) gamma ray Observatory to indirectly search for dark matter (DM) by studying gamma ray emission from dwarf spheroidal galaxies (dSphs). Selected for their high ratio of dark matter to baryonic matter, dSphs are useful for this type of search owing to the low background emission. In comparison to previous HAWC studies, we significantly improve our sensitivity to DM from dSphs due to improvements to our event reconstruction and reduced hadronic contamination. We expanded the number of dSphs studied, DM annihilation channels into the Standard Model (SM), and the amount of data collected on each previously studied dSph. We searched for DM signals in each dSph using the latest version of the algorithms used to reconstruct data from the primary detector of the HAWC instrument. We report that we do not detect evidence of DM from dSphs, so we place upper limits for the velocity-weighted DM annihilation cross-section ($$\langle\sigma v \rangle$$) on the order of $$10^{-23}~\text{cm}^3\text{s}^{-1}$$ for a DM mass range of $$1-10^4$$ TeV.
Dwarf spheroidal galaxies are almost entirely dark matter — ordinary matter makes up less than one percent of them. They are the darkest known places in the universe.