Researchers have identified a rare cosmic engine within the Milky Way capable of accelerating protons to extreme energy levels. This object, known as LHAASO J1912+1014u, functions as a proton PeVatron, pushing particles beyond one quadrillion electron volts. This finding provides critical data on the origin of cosmic rays that travel through interstellar space.
An international team led by Hiroshima University confirmed the nature of this source by combining data from several observatories. Identifying these accelerators is difficult because scientists must distinguish between signals from protons and those from high-energy electrons. Previous surveys detected gamma-ray sources, but existing resolution was insufficient to determine the mechanism behind them.
To solve this, the team integrated observations from the Fermi Large Area Telescope, the FUGIN radio survey, and the Chandra X-ray Observatory. By modeling the source across the electromagnetic spectrum, they ruled out alternative explanations. The data showed that the gamma-ray signal remains smooth across a wide energy range, a hallmark of proton acceleration. Furthermore, the correlation between GeV gamma rays and interstellar gas density pointed directly to proton interactions.
The weak X-ray emission detected by Chandra provided the final piece of evidence. If electrons were driving the activity, the X-ray signals would be much stronger. Because these emissions were faint, the team concluded that protons are the primary particles reaching these massive energy thresholds. This discovery marks a step forward in understanding the natural particle accelerators scattered throughout our galaxy.
Future research will focus on analyzing other candidates for proton PeVatrons. With dozens of similar objects identified in the Milky Way, the team aims to categorize the types of cosmic events that produce these high-energy particles. This multi-observatory approach serves as a framework for future studies in high-energy astrophysics.