Washington, Nov 29 (ANI): 'Super bubbles' in space could be the main source of high-energy cosmic rays striking the earth, a new study has revealed.
The new study has suggested that Gamma-ray emission detected by Fermi LAT fills bubbles of hot gas created by the most massive stars in the constellation Cygnus X.
The turbulence and shock waves produced by these stars make it more difficult for high-energy cosmic rays to traverse the region. When the particles strike gas nuclei or photons of starlight, gamma rays result.
Astronomers viewing the region at visible wavelengths see only hints of this spectacular activity thanks to a veil of nearby dust clouds forming the Great Rift, a dark lane that splits the Milky Way, a faint band of light marking our galaxy's central plane.
A study using data from NASA's Fermi Gamma-ray Space Telescope finds that the tumult of star birth and death in Cygnus X has managed to corral fast-moving particles called cosmic rays.
When cosmic rays collide with interstellar gas, they produce gamma rays. By tracing gamma-ray signals throughout the galaxy, Fermi's Large Area Telescope (LAT) is helping astronomers understand the sources of cosmic rays and how they're accelerated to such high speeds.
The galaxy's best candidate sites for cosmic-ray acceleration are the rapidly expanding shells of ionized gas and magnetic field associated with supernova explosions.
For stars, mass is destiny, and the most massive ones, known as types O and B, live fast and die young.
Astronomers estimate that the association's total stellar mass is 30,000 times that of our sun, making Cygnus OB2 the largest object of its type within 6,500 light-years. And with ages of less than 5 million years, few of its most massive stars have lived long enough to exhaust their fuel and explode as supernovae.
Intense light and outflows from the monster stars in Cygnus OB2 and from several other nearby associations and star clusters have excavated vast amounts of gas from their vicinities.
The stars reside within cavities filled with hot, thin gas surrounded by ridges of cool, dense gas where stars are now forming.
It's within the hollowed-out zones that Fermi's LAT detects intense gamma-ray emission.
"We are seeing young cosmic rays, with energies comparable to those produced by the most powerful particle accelerators on Earth," said co-author Luigi Tibaldo, a physicist at Padova University and the Italian National Institute of Nuclear Physics.
"They have just started their galactic voyage, zig-zagging away from their accelerator and producing gamma rays when striking gas or starlight in the cavities."
"These shockwaves stir the gas and twist and tangle the magnetic field in a cosmic-scale jacuzzi so the young cosmic rays, freshly ejected from their accelerators, remain trapped in this turmoil until they can leak into quieter interstellar regions, where they can stream more freely," said co-author Isabelle Grenier.
The Fermi team considers it possible that the supernova remnant spawned the cosmic rays trapped in the Cygnus X 'cocoon', but they also suggest an alternative scenario where the particles became accelerated through repeated interaction with shockwaves produced inside the cocoon by powerful stellar winds.
"Whether the particles further gain or lose energy inside this cocoon needs to be investigated, but its existence shows that cosmic-ray history is much more eventful than a random walk away from their sources," Tibaldo added.
The study has been recently published in the journal Science. (ANI)
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