Milky Way’s Particle Accelerators

Researchers from the Astronomical Institute at Utrecht University have been observing the Milky Way’s particle accelerators. Using data from NASA’s Chandra X-Ray Observatory and European Southern Observatory’s (ESO) Very Large Telescope, the researchers have determined that cosmic rays from our galaxy are very efficiently accelerated in the remnants of exploded stars.

Astronauts from the Apollo space endeavours described seeing odd flashes of light that were even visible with their eyes closed. Scientists have clarified that these flashes were cosmic rays; energetic particles emanating from outside the solar system. Cosmic rays constantly bombard earth’s atmosphere and have enough energy to negatively affect electronic components.

The protons in cosmic rays move at the speed of light which is also the maximum speed limit in the Universe. The protons accelerate to such high energies that even CERN’s Large Hadron Collider cannot replicate such conditions. “It has long been thought that the super-accelerators that produce these cosmic rays in the Milky Way are the expanding envelopes created by exploded stars, but our observations reveal the smoking gun that proves it”, says Eveline Helder who is the lead author of the study.

The team has developed a measurement to calculate a long standing uncertainty of whether stellar explosions can produce an adequate number of accelerated particles and to explain the volume of cosmic rays to hit the atmosphere. The study also outlines the level of energy from shocked gas that is used to accelerate particles during the stellar explosion of a star.

“When a star explodes in what we call a supernova a large part of the explosion energy is used for accelerating some particles up to extremely high energies”, says Helder. “The energy that is used for particle acceleration is at the expense of heating the gas, which is therefore much colder than theory predicts”.

The researchers used the example of a star called RCW 86 that exploded in AD185. Ancient Chinese astronomers recorded this explosion, located 8200 light-years away. The researchers measured the gas right behind the shockwave created by the stellar explosion using data from ESO’s Very Large Telescope and images captured by NASA’s Chandra X-ray Observatory. The results showed the particles to be moving at an astonishing 10 to 30 million kilometres per hour.

The gas was shown to have a temperature of 30 million degrees Celsius, which is impossible to replicate on Earth. However, scientists expected the shockwaves temperature to be around half a billion degrees given the high velocities apparent. “The missing energy is what drives the cosmic rays”, concludes Helder.

Icon image caption: Images show low energy X-rays in red, medium energies in green and high energies in blue. The Chandra observations focused on the northeast (left-hand) side of RCW 86, and show that X-ray radiation is produced both by high-energy electrons accelerated in a magnetic field (blue) as well as heat from the blast itself (red). (Credit: Chandra X-ray Observatory)

TFOT has previously written an article titled “Cosmic Rays from Nowhere”, in which we have covered the discovery of a mysterious object close to our solar system, which was detected by an international team of scientists, who made the discovery after exploring an unusual surplus of high-energy electrons bombarding the Earth from outer space. You are also welcome to check out our recent article on debris from colliding galaxies. Be also sure to check out our coverage of the CERN Large Hadron Collider (LHC).

More information, including images and other multimedia, can be found at the Harvard and NASA websites.

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