Technology & Science
LHAASO Ties Milky Way’s 3 PeV “Knee” to Black-Hole Micro-Quasar Jets
On 16 Nov 2025, China’s LHAASO observatory published twin papers showing that jets from five micro-quasars accelerate particles past 3 PeV, empirically linking the 70-year-old ‘knee’ in the cosmic-ray spectrum to black-hole systems.
Focusing Facts
- LHAASO detected ≥0.8 PeV gamma-rays from SS 433, V4641 Sgr, GRS 1915+105, MAXI J1820+070, and Cygnus X-1, implying parent protons >10 PeV.
- Using multi-parameter air-shower techniques, LHAASO isolated a high-purity proton sample and measured an unexpected new high-energy component above the 3 PeV knee.
- Separately, XMM-Newton data led MSU researchers (Apr 2025 ApJ) to classify PeVatron 1LHAASO J0343+5254u as a pulsar-wind-nebula cosmic-ray source.
Context
Astrophysicists have chased cosmic-ray origins since Victor Hess’s balloon flights in 1912 and the first ‘knee’ reports in 1958. Just as the 1963 discovery of quasars rewrote models of galactic nuclei, LHAASO’s micro-quasar result—enabled by a 4,410 m-high, 1-km² detector finished in 2023—shifts attention from long-favoured supernova remnants to compact black-hole binaries. It fits a broader 21st-century trend: ever-larger, ground-based arrays (IceCube 2013 PeV neutrinos, HAWC 2019 TeV map) revealing multiple accelerator populations and suggesting a Galactic ‘ecology’ of sources with distinct energy ceilings. Over a century scale, pinning the knee to micro-quasars narrows the parameter space for dark-matter models, informs next-generation terrestrial accelerators that mimic jet physics, and underscores how scientific leadership oscillates geographically—recalling how the 1930s U.S. cyclotrons supplanted Europe, today China’s LHAASO challenges Western observatories. Whether further multi-messenger campaigns (neutrinos, X-rays) confirm a dozen such PeVatrons will determine if this is a paradigm shift or merely another step in a quest likely to outlast current instruments.
Perspectives
US-based popular science media
e.g., SciTechDaily — Highlights new Michigan State University work that pins at least one PeV cosmic-ray accelerator on a pulsar-wind nebula, reinforcing the idea that super-energetic particles mainly originate in varied stellar remnants rather than black-hole jets. Focuses on U.S. university research funded by NASA/NSF and never mentions the high-profile Chinese LHAASO results published the same week, so readers may come away thinking the pulsar-wind-nebula route is the leading—or only—breakthrough.
Chinese state-owned and aligned outlets
e.g., China Daily, Global Times — Trumpets LHAASO’s detection of micro-quasar black-hole jets as the long-sought explanation for the cosmic-ray “knee,” declaring the mystery solved and underscoring China’s leadership in high-energy astrophysics. National-pride framing and repetition of press-release language downplay alternative accelerators such as pulsar nebulae or supernova remnants and present the result as definitive despite it still being one competing hypothesis.