Accession Number:

ADA523017

Title:

Cosmic Rays from Gamma Ray Bursts in the Galaxy

Descriptive Note:

Journal article

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC SPACE SCIENCE DIV

Personal Author(s):

Report Date:

2005-01-01

Pagination or Media Count:

4.0

Abstract:

Gamma-ray bursts GRBs are brief flashes of gamma-ray light emitted by sources at cosmological distances. Recent observations link GRBs with star-forming galaxies and a rare type of evolved high-mass star that explodes as a supernova when its core collapses to a black hole. Most core-collapse supernovae, by contrast, form neutron stars. In either case, the supernova explosion ejects a remnant that expands into and shocks the interstellar medium. These shock waves accelerate high-energy cosmic-ray protons and ions. The supernovae that form neutron stars are thought to accelerate cosmic rays to energies reaching 1014 eV. The much more energetic GRB shock waves, with speeds very close to the speed of light, are thought to accelerate the highest energy cosmic rays, with energies reaching and exceeding 1020 eV. Because the Milky Way is actively making young high-mass stars, GRBs will also occur in our Galaxy. The rate of GRBs in the Milky Way is very uncertain because of the lack of precise knowledge about the opening angle of GRB jets, but it could be as frequent as once every 10,000 years. Acceleration of cosmic rays by GRB jets, and propagation of cosmic rays through the magnetic field of our Galaxy and across the universe, can explain the spectrum of cosmic rays at the highest energies. Over the age of the Galaxy, there is a good chance that a nearby powerful GRB, with a jet oriented toward Earth, could have lethal consequences for life. It has recently been argued that such an event contributed to the Ordovician extinction event 440 M yrs ago. Understanding cosmic ray propagation and effects on materials is important to estimate radiation damage on spacecraft, cosmic ray effects on humans in space and the origin of cosmic rays.

Subject Categories:

  • Astrophysics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE