Black Hole Jets Solve Decades-Old Cosmic Ray Mystery, Chinese Observatory Reveals
A groundbreaking study utilizing data from China’s Large High Altitude Air Shower Observatory (LHAASO) has, for the first time, linked the enigmatic “knee” in the cosmic ray energy spectrum to powerful particle acceleration within micro-quasars – systems fueled by black holes. This revelation, announced Sunday, resolves a nearly 70-year-old puzzle and offers crucial insights into the origins of high-energy cosmic rays.
The “knee” represents a critical point in understanding these sources, marking a boundary between lower-energy cosmic rays and the more elusive, ultra-high-energy particles. Previously, sources like supernova remnants were considered potential candidates, but struggled to explain the observed energy levels.
LHAASO’s observations have changed that. The observatory systematically detected ultra-high-energy gamma rays emanating from five micro-quasars,revealing that these systems are capable of accelerating particles to energies exceeding 1 PeV – and even reaching 10 PeV. This surpasses the energy threshold of the “knee,” effectively eliminating the limitations of previously considered sources.
“This finding addressed the long-standing issue that the previously recognized cosmic ray sources…couldn’t surpass this threshold either observationally or theoretically,” a senior official stated.
LHAASO’s Breakthrough Technology
The success of this research hinges on LHAASO’s unique capabilities. Located at an altitude of 4,410 meters on Mount Haizi in Sichuan Province, China, the observatory employs a “hybrid detector array” designed to detect both ultra-high-energy gamma rays and cosmic ray particles. This allows for a thorough analysis of cosmic phenomena.
A key challenge in studying the “knee” has been distinguishing protons – a major component of cosmic rays – from heavier nuclei. Due to the rarity of cosmic rays in this energy range and interference from Earth’s atmosphere, this was previously considered impractical. Though, LHAASO’s advanced “multiparameter measurement techniques” enabled the research team to obtain a large sample of high-purity protons wiht unprecedented precision.
This analysis revealed a previously unknown structure in the energy spectrum – a “high-energy component” that further supports the micro-quasar origin theory. The findings, combined with data from space-borne experiments, demonstrate the existence of multiple populations of cosmic ray accelerators within the Milky Way, each with its own energy range and acceleration capabilities.
Implications for Astrophysics and Particle Physics
The discovery has far-reaching implications. It not only resolves the mystery of the “knee” but also provides crucial observational evidence for the role of black holes in the origin of cosmic rays. According to Cao Zhen, an academician of the Chinese Academy of Sciences (CAS) and chief scientist of LHAASO, the observatory has, for the first time, observationally connected the “knee” structure to a specific astrophysical source – the black hole jet system.
“It is indeed estimated there are a dozen or so such sources in our Galaxy,” Cao told the Global Times on Sunday.
Furthermore, Cao noted a surprising parallel between the mechanisms driving cosmic ray acceleration and those used in artificial accelerators, suggesting potential applications for the next generation of particle physics technology. understanding these processes could lead to advancements in our ability to create and control high-energy particles.
LHAASO’s success underscores China’s growing leadership in high-energy cosmic ray research. The observatory’s sensitivity in both gamma-ray astronomy and cosmic ray precision measurement has already yielded a series of globally impactful discoveries, contributing substantially to our understanding of the universe’s most extreme physical processes.
