Probably the most energetic cosmic-ray electrons ever detected are giving us some very important clues as to the origins of those enigmatic particles.
Since 2015, greater than 7 million particles have hit the CALorimetric Electron Telescope (CALET) strapped to the sturdy, broad again of the Worldwide Area Station.
This huge assortment has given scientists a sturdy dataset that, they are saying, factors to no less than one close by supply of cosmic-ray electrons – and probably extra.
“The most exciting part is seeing things at the highest energies,” says astrophysicist Nicholas Cannady of the College of Maryland Baltimore County, and member of the CALET Collaboration led by astrophysicist Shoji Torii of the College of Waseda in Japan.
“We have some candidates above 10 teraelectronvolts – and if it is borne out that these are real electron events, it’s really a smoking gun for clear evidence of a nearby source.”
We have identified about energetic cosmic rays since indicators of their presence have been first observed over a century ago, and for all that point, their supply has largely remained a thriller.
They’re tiny particles – largely atomic nuclei, but additionally sub-nuclear particles corresponding to protons and electrons – streaming via the Universe at near the velocity of sunshine, with extra energy than these little issues ought to have.
Like most energetic issues within the Universe, although, scientists suppose they arrive from energetic sources. The more than likely clarification up to now is supernova remnants, which speed up particles and ship them zooming via area, however there are different attainable sources, too.
One among these is the theoretical annihilation of dark matter, so physicists are eager to check them and perceive their origin. However detecting them is a bit tough. Here on Earth, cosmic rays collide with atoms and molecules within the ambiance and produce showers of particles; it is the bathe we detect, not the cosmic ray itself.
Some high-energy electron detectors additionally undergo from interference from quick flying protons messing with the outcomes. However the space-based CALET experiment permits for direct detection of cosmic rays, as much as excessive energies.
Earlier work allowed for the detection of cosmic rays up to 4.8 teraelectronvolts. That work discovered that, as vitality ranges elevated, the variety of cosmic rays fell.
Utilizing CALET’s enormous pool of knowledge with new processes to sift out errors attributable to interfering protons, the staff have been in a position to detect electron cosmic rays as much as 7.5 teraelectronvolts, vastly growing the vary of the information.
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And, interestingly, they found that there was no fall in cosmic ray incidence at higher energies. If anything, the opposite appears to be true: at the highest energies, cosmic rays seem to increase.
We still don’t know where they’re coming from, but, since cosmic rays lose energy as they travel through space, the high energies suggest that they must be coming from relatively close to us.
In fact, there are supernova remnants nearby whose location and proximity is consistent with the detection of some of the highest-energy cosmic rays detected in the dataset. The team hopes that continued observation will elucidate the origin further.
“These CALET observations open the tantalizing chance that matter from a specific close by supernova remnant could be measured at Earth,” says physicist T. Gregory Guzik of Louisiana State University, leader of the US branch of the CALET Collaboration.
“Continued CALET measurement via the lifetime of the Worldwide Area Station will assist shed new mild on the origin and transport of relativistic matter in our galaxy.”
The analysis has been printed in Physical Review Letters.
