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 Nov 2015
The next Google Hangout in our Future in Space series is today at 3:00 pm ET »  Details
20 Nov 2015
Application for Athena Working Group membership is now reopened. »  Details
5 Nov 2015
New! PhysPAG Executive Committee Selections November 2015 »  [PDF]
8 Oct 2015
Final PhysPAG Response to Paul Hertz, October 8, 2015 now available »  [PDF]

Project News

Chandra News
23 Sep 2015
Milky Way's Black Hole Shows Signs of Increased Chatter » Details
Fermi News
18 Aug 2015
Sixth International Fermi Symposium » Details
Planck News
31 Mar 2015
Herschel and Planck find missing clue to galaxy cluster formation
» Details
XMM-Newton News
20 Aug 2015
The Tumultuous Heart of Our Galaxy » Details

Related News

8 Jul 2015
Searing Sun Seen in X-rays » Details
Suzaku News
2 Apr 2015
Suzaku Studies Supernova 'Crime Scene,' Shows a Single White Dwarf to Blame » Details
Swift News
9 Jul 2015
NASA's Swift Reveals a Black Hole Bull's-eye » Details