Astronomers have long searched for the launch sites of some of the most energetic protons in our galaxy. Now, a study using years of data from NASA’s Fermi Gamma-Ray Space Telescope confirms that a supernova remnant is exactly such a place.
Fermi showed that shock waves from exploded stars propel particles at speeds comparable to the speed of light. Called cosmic rays, these particles mostly take the form of protons, but can include atomic nuclei and electrons. Because they all carry an electric charge, their paths blur as they pass through our galaxy’s magnetic field. As it is no longer known which way they originated, this obscures their place of birth. But when these particles collide with interstellar gas near the supernova remnant, they produce a telltale glow in gamma rays – the most energetic light there is.
“ Theorists believe that the most energetic cosmic ray protons in the Milky Way reach one million billion electron volts, or PeV energies,” said Ke Fang, assistant professor of physics at the University of Wisconsin at Madison. “The precise nature of their sources, which we call PeVatrons, has been difficult to pinpoint.”
Trapped by chaotic magnetic fields, the particles repeatedly pass through the waveform. supernova shock, gaining speed and energy with each pass. Eventually, the remnant can no longer hold them back and they fly off into interstellar space.
Boosted to approximately 10 times the energy gathered by the world’s most powerful particle accelerator, the Big Hadron Collider, PeV protons are on the verge of completely escaping from our galaxy.
Astronomers have identified a few suspicious PeVatrons, including one at the center of our galaxy. Naturally, supernova remnants top the list of candidates. Yet, out of approximately 106 known remains, only a few emit gamma rays with sufficiently high energies.
One stellar wreckage in particular has garnered much attention from the gamma serving astronomers. Called G106.3 + 2.7, it is a comet-shaped cloud located at approximately 2 12 light years in the constellation Cepheus. A bright pulsar caps the northern end of the supernova remnant, and astronomers believe the two objects formed in the same explosion.
The Fermi Large Area Telescope, its primary instrument, has detected one billion electron-volt (GeV) gamma rays originating from inside the extended tail rest. (For comparison, the energy of light seen measures between approximately 2 and 3 electron-volts.) The Quite Energetic Radiation Imaging Telescope Array System (VERITAS) at the Fred Lawrence Whipple Observatory in southern Arizona recorded even more energetic gamma rays from the same region. have to prove that it accelerates protons,” explained co-author Henrike Fleischhack of the Catholic University of America in Washington and NASA’s Goddard Space. Flight Center in Greenbelt, Maryland. “The problem is that electrons accelerated to a few hundred TeV can produce the same emission. Now, with the help of years of Fermi data, we believe we have demonstrated that G.3+2.7 is indeed a PeVatron.”
A write-up detailing the results, edited by Fang, was published on 10 August in the journal Actual physical Evaluation Letters.
Le pulsar, J2229+6114, emits its own gamma rays in a lighthouse-like beacon as it spins, and this glow dominates the region at energies of a few GeV. Most of this emission occurs in the first half of the pulsar’s rotation. The team effectively extinguished the pulsar by analyzing only gamma rays from the latter part of the cycle. Below 10 GeV, there is no significant emission from the remainder tail.
Above this energy, the interference from the pulsar is negligible and the additional resource becomes readily apparent. The team’s detailed analysis overwhelmingly favors PeV protons as the source particles for this gamma ray emission.
“So far, G106.3+2.7 is distinctive, but it might turn out to be the member the brightest of a new population of supernova remnants that emit gamma rays reaching TeV energies,” be aware Fang. “Furthermore of them could be revealed thanks to future observations from Fermi and very high energy gamma-ray observatories.”
Video: https://youtu.be/ oYm-0MX_3HE