The night sky looks calm, but in reality, invisible particles, cosmic rays, are constantly flying through us. Among them are electrons and their antimatter counterparts, positrons. When they collide with detectors on satellites or balloons, the instruments record their energy. And here lies the mystery: on a graph with energy on the horizontal axis and the number of particles on the vertical axis, you see not smooth lines but breaks and bumps. As if someone had added extra particles with specific energies to the overall stream.
To figure this out, researchers built a model in which cosmic electrons come from two sources. The first is a diffuse background: particles wandering through the Galaxy, gradually gaining energy from supernova explosions. The second is specific nearby objects, such as pulsars. A pulsar is a rapidly rotating neutron star that, like a lighthouse, sends out beams of radiation. Near such a lighthouse, electrons can be accelerated to enormous speeds. The scientists calculated how these particles travel to us, losing energy along the way due to interactions with light and magnetic fields.
It turned out that if you take into account not only the steady stream from a pulsar but also possible one-off outbursts, you can reproduce those very breaks in the spectrum. Particularly interesting are data from the Chinese satellite DAMPE, which measured energies up to several trillion electron-volts — thousands of times higher than the energy of particles in the Large Hadron Collider. The model with nearby pulsars fits these data points well. This means that to explain the observations, we don't need hypotheses about dark matter decay or other exotic processes — ordinary astrophysical sources suffice.
This approach helps distinguish the "ordinary" from the "unusual." If future data show a break that doesn't fit the pulsar model, that would be a signal to search for new physical phenomena. For now, the night sky continues to send us its encoded messages, and we are learning to read them.
as written by the authors arXiv:2608.09336v1
Precise measurements of high-energy cosmic-ray electrons and positrons have revealed spectral structures that are difficult to capture with a single smooth power-law background. The rising positron fraction measured by PAMELA and AMS-02, together with the all-electron excess reported by ATIC and the high-precision all-electron spectrum measured by DAMPE, has motivated interpretations ranging from nearby astrophysical accelerators to dark-matter annihilation or decay. In this work we revisit the conventional diffuse electron background and the possible contribution from nearby pulsars in a common propagation framework. The diffuse component is modeled with GALPROP configurations calibrated by cosmic-ray nuclei and diffuse gamma-ray observations. We then use the Green-function solution for nearby discrete sources with radiative losses to study pulsar contributions with both burst-like and continuous injection histories, including the effect of stochastic inverse-Compton cooling on the propagated spectra. We also use the highest-energy DAMPE data points as an illustrative case to compare possible local-source contributions from pulsars and supernova-remnant-like burst sources. The spectral shape of such features provides a useful diagnostic for distinguishing physically plausible nearby-source features from more exotic interpretations.
The energy of the fastest cosmic electrons can be billions of times higher than the energy of particles in medical accelerators, yet they are produced naturally in the vicinity of pulsars.