Science Goals

Explore the behavior of matter and energy in its most extreme environments

Cosmic rays, high-energy charged particles traveling at velocities that can approach the speed of light, are a rich potential probe of chemical and nuclear in the Universe. The majority of cosmic rays are atomic nuclei from hydrogen to the heaviest elements with energies spanning more than twelve orders of magnitude. In the low energy end, these cosmic rays are most likely accelerated in supernova remnants. Their elemental and isotopic composition probes nucleosynthesis, nuclear interactions with the interstellar medium, the distribution of freshly synthesized elements, and the mechanism of supernova explosions. At energies above roughly 1017 eV a different source dominates. The acceleration engines responsible for such extreme energies are not well understood, but at the highest energies, above about 6 × 1019 eV, the rapid energy loss resulting from interactions with the cosmic microwave background limits sources to within about 100 Mpc. Other cosmic ray components include electrons, positrons and antiprotons. While these are largely the result of interactions of nuclear cosmic rays with the ISM, they may have other origins. Positrons and electrons can be produced directly in astrophysical objects such as pulsars and deviations in their spectra can provide important insights into nearby sources. Cosmic ray particles may also be produced directly by the annihilation of dark matter candidates such as nutralinos and Kaluza-Klein particles. Details of the spectra of the resulting particles would therefore provide important constraints on the nature of the dark matter.

Program News

20 Mar 2017
Astrophysics Probe mission studies selected (3/20/2017) »  [PDF]
6 Mar 2017
Terms of Reference (ToR) for the PhysPAG have been updated. »  [PDF]
23 Feb 2017
Self-nominations for the Astrophysics Advisory Committee (APAC, replaces the Astrophysics Subcommitte or APS) are requested; due date is 8 March 2017.
»  Details

Project News

Chandra News
14 Feb 2017
Black-Hole-Powered Jets Forge Fuel for Star Formation » Details
Fermi News
30 Jan 2017
NASA's Fermi Discovers the Most Extreme Blazars Yet » Details
NASA's Fermi Sees Gamma Rays from 'Hidden' Solar Flares » Details
Planck News
13 Aug 2016
First Stars Formed Even Later Than Previously Thought
» Details
XMM-Newton News
31 Jan 2017
Mind the Gap: Rapid Burster behaviour explained » Details

Related News

Hitomi News
6 July 2016
Hitomi Mission Charts Hot Winds of a Galaxy Cluster for the First Time »  Details
NuSTAR News
31 Jan 2017
NuSTAR Helps Solve 'Rapid Burster' Mystery » Details
Suzaku News
26 Aug 2015
X-ray Astronomy Satellite "Suzaku" Completes Scientific Mission » Details
Swift News
7 Feb 2017
Goddard Center Director Remarks on Passing of Neil Gehrels » Details