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The cosmic rays that bombard Earth are not coming from where we thought, scientists say – and we might have found their source.
For decades, researchers have believed that cosmic rays that arrive on Earth from the edges of the galaxy start in stars that go into supernovae. It happens when they get so big that they are unable to support their own hearts and they explode.
Researchers can be sure that such cosmic rays are reaching us – and at such high speeds – thanks to experiments such as the High-Altitude Water Cherenkov Observatory (HAWC) near Puebla, Mexico, which uses large reservoirs of water that ignite when struck by high energy particles.
But scientists are now saying that these high-energy particles don’t appear to be from supernovae, because they aren’t powerful enough to do so with the huge amounts of energy that have been observed. Even though supernovae can destroy an entire solar system, they lack the power to hit us with such energetic rays, the researchers say.
Instead, the fast-paced cosmic rays actually appear to come from star clusters that act as accelerators and launch the particles across the galaxy with such intense amounts of energy, according to new research.
Papers describing the new findings, which the researchers describe as a paradigm shift, have been published in Nature astronomy and Letters from the Astrophysical Journal.
Although these rays have been presumed to originate from supernova remnants, the researchers say this is theoretically difficult to explain, and there is no evidence that the highly energetic cosmic rays originate from these supernovae.
The researchers had already seen clues that it could be star clusters that were in fact responsible. But they have now seen confirmation that they are able to do so, in work that examined the Cygnus Cocoon, a “superbubble” that surrounds an area where massive stars form.
Such star-forming regions appear to be prime candidates for “PeVatrons,” according to the researchers. (PeVatrons is the name for PeV accelerators, with petaelectronvolts or PeVs being a marker for the amount of energy needed to move particles at such high speeds.)
“There have been several other clues that star clusters could be a part of history,” Henrike Fleischhack, one of the study’s researchers, said in a statement. “Now we are getting confirmation that they are able to go to the higher energies.”
Star clusters are made up of the remains of a supernova. They are also known as Star Cradles and are made up of winds and clouds of debris gathered in violent and extreme space areas.
As the name suggests, they are filled with hundreds of stars which are clustered together in a very limited number of space: Hundreds of massive objects known as spectral type O and type B are gathered in areas of just over 100 light years.
It is between these stars that cosmic rays are projected across the universe.
“O-type spectral stars are the most massive,” said Binita Hona, another of the many researchers on the new papers. “When their winds interact with each other, shock waves are formed, which is where the acceleration occurs.”
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