Cosmic ray puzzle resolved as scientists hyperlink ‘knee’ formation to black holes

Milestone outcomes launched by the Massive Excessive Altitude Air Bathe Observatory (LHAASO) on November 16 have solved a decades-old thriller in regards to the cosmic ray vitality spectrum—which exhibits a pointy lower in cosmic rays above 3 PeV, giving it an uncommon knee-like form.

The reason for the “knee” has remained unclear since its discovery practically 70 years in the past. Scientists have speculated that it’s linked to the acceleration restrict of the astrophysical sources of cosmic rays and displays the transition of the cosmic ray vitality spectrum from one power-law distribution to a different.

Now, nevertheless, two latest research—printed in Nationwide Science Evaluation and Science Bulletin, respectively—display that micro-quasars pushed by black gap system accretion are highly effective particle accelerators within the Milky Means and are the possible supply of the “knee.” The research additionally advance our understanding of the intense bodily processes of black gap programs.

The analysis was performed by researchers from the Institute of Excessive Power Physics of the Chinese language Academy of Sciences (CAS), Nanjing College, the College of Science and Expertise of China of CAS, La Sapienza College of Rome, and different establishments.

Micro-quasars recognized as cosmic accelerators

Black holes, one of the enigmatic objects within the universe, generate relativistic jets when accreting materials from companion stars in binary programs, forming “micro-quasars.” On this research, LHAASO systematically detected for the primary time ultra-high-energy gamma rays from 5 micro-quasars: SS 433, V4641 Sgr, GRS 1915+105, MAXI J1820+070, and Cygnus X-1.

Specifically, the ultra-high-energy radiation from SS 433 was discovered to overlap with an enormous atomic cloud, strongly suggesting that the high-energy protons are accelerated by the black gap and collide with surrounding matter.

The proton vitality on this system exceeded 1 PeV, with a complete energy output of roughly 10³² joules per second, equal to the vitality launched per second by 4 trillion of probably the most highly effective hydrogen bombs. The gamma-ray vitality from V4641 Sgr was discovered to succeed in 0.8 PeV, making it one other “tremendous PeV particle accelerator,” whereas the mum or dad particles producing these gamma rays had energies exceeding 10 PeV.

These outcomes show that micro-quasars are vital PeV particle accelerators within the Milky Means, addressing a long-standing situation in science: Whereas supernova remnants had been traditionally acknowledged as cosmic ray sources, each observational and theoretical studies have proven that they can not speed up cosmic rays to the energies of the “knee” and past.

Challenges in measuring cosmic ray spectra

To totally perceive this phenomenon, exact measurements of the vitality spectra of the varied cosmic ray species together with their respective “knees” are important. Step one is to measure the vitality spectrum of the lightest nuclei—protons. Nevertheless, cosmic rays within the “knee” area are sparse and satellite tv for pc detectors have restricted acceptance, making detection akin to discovering a needle in a haystack.

In ground-based oblique measurements of cosmic ray particles, it’s unimaginable to keep away from atmospheric interference. This makes it troublesome to tell apart protons from different nuclei. For a very long time, this measurement was thought of unimaginable.

On this research, leveraging its world-leading ground-based cosmic ray observational tools, LHAASO developed multi-parameter measurement methods and chosen a big statistical pattern of high-purity protons, permitting for exact measurement of their vitality spectrum, with precision akin to that of satellite tv for pc experiments. This measurement revealed an vitality spectrum construction that was solely sudden, clearly displaying a brand new “high-energy element” as a substitute of a easy transition between power-law spectra.

A number of accelerators form cosmic ray origins

LHAASO’s new findings, along with the low-energy element measured by the space-borne AMS-02 experiment and the intermediate-energy element measured by the space-borne DArk Matter Particle Explorer (DAMPE) experiment, revealed the existence of a number of accelerators throughout the Milky Means, with every possessing its personal distinctive acceleration functionality and vitality vary. The “knee” represents the acceleration restrict of the sources liable for producing the high-energy element.

The advanced construction of the proton vitality spectrum signifies that cosmic ray protons within the PeV vitality vary primarily originate from “new sources” resembling micro-quasars, which have an acceleration restrict considerably increased than that of supernova remnants. This permits them to generate high-energy cosmic rays that exceed the “knee.”

Breakthroughs join black holes to cosmic rays

These two discoveries assist one another, presenting a complete scientific image. This not solely marks a big development in resolving the long-standing thriller of the “knee” origin, but additionally affords essential observational proof for understanding the function of black holes within the origin of cosmic rays.

LHAASO’s hybrid detector array design permits for the detection of cosmic ray sources by ultra-high-energy gamma rays, whereas enabling exact measurement of cosmic ray particles within the neighborhood of the photo voltaic system. This method affords insights into the acceleration capabilities of sources at PeV energies and the spectral traits they contribute to cosmic rays. For the primary time, the “knee” construction has been observationally related to a particular sort of astrophysical supply—the black gap jet system.

LHAASO, which was designed, constructed, and is operated by Chinese language scientists, has taken the lead in high-energy cosmic-ray analysis as a result of its sensitivity in each gamma ray astronomical exploration and cosmic ray precision measurement. It has achieved a collection of discoveries which have a world influence, thereby contributing to our data of the intense bodily processes within the universe.