Composite infrared, optical, and X-ray image of a remnant of an exploded star, first sighted by Johannes Kepler some 400 years ago. The shrapnel of the star collide with the ambient interstellar gas, providing conditions to accelerate cosmic particles to enormous energies.
Image credit: NASA's Chandra X-ray Observatory, Hubble Space Telescope, and Spitzer Observatory
The universe is awash in highly energetic particles with velocities approaching the speed of light. Though these particles exist in many places throughout the universe – and can even be found slamming into our own atmosphere – scientists don’t yet fully understand their origins.
Nature’s High-Performance Accelerator
Celestial objects such as neutron stars or the remnants of exploded stars eject particles with energies exceeding the capability of the best accelerators on Earth by a factor of a thousand or more. Known as cosmic rays, these high-energy particles are capable of reaching Earth where they are studied either by satellite-based detectors, or from the ground with instruments that examine their interaction with the Earth’s atmosphere.
Though scientists have developed provisional models to explain the behavior of these particles, the mechanisms that underlie their acceleration are not fully understood. Scientists speculate, however, that explosions of massive stars, known as supernovae, and the resulting shock waves sent into the surrounding interstellar gas may provide the motive force. There is also emerging consensus that magnetic fields play a role in helping these particles achieve their enormous energies.
Understanding Natural Particle Acceleration Source
Scientists face significant challenges in seeking to identify and understand the sources of these highly energetic particles. The equations are highly complex and observations require precise instruments such as the Fermi Gamma-ray Space Telescope. Eventually, scientists may be able to use data from Fermi and other instruments to better understand these particles and build more powerful and efficient accelerators to replicate them on Earth.