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PCOS 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 the only direct probe of chemical composition and nuclearsynthesis 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. Cosmic rays with energies below and just above the so-called "knee" in the middle of this energy range are most likely accelerated in supernova remnants. Their elemental and isotopic composition probes nucleosynthesis, nuclear interactions in the interstellar medium, the distribution of freshly synthesized elements, global Galactic properties, the mechanisms of supernova explosions, and particle acceleration in supernova shocks. 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 6 x 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. Electrons are quite abundant and can be accelerated in many different types of sources, while positrons and antiprotons are largely the result of interactions of nuclear cosmic rays with the ISM but may also have other origins. Positrons as well as 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 in the annihilation of dark matter candidate particles such as, e.g., WIMPs, neutralinos, and Kaluza-Klein particles. Details of the spectra and composition of the resulting particles therefore provide important insights into the physics of particle accelerators and properties of the interstellar and/or intergalactic medium, and provide important constraints on the nature of the dark matter.

The European Space Agency LISA observatory


Program News and Announcements

18 January 2021
Meeting of Astronomy and Astrophysics Advisory Committee (AAAC) on 26–27 January 2021 »  Details.
14 January 2021
NuSTAR General Observer Cycle 7 Proposal Deadline 29 January 2021 »  Details.
6 January 2021
Draft Astrophysics Explorers Program Solicitations Released for Community Comment for Solicitations for both Medium Explorer (MIDEX) and Missions of Opportunity (APEXMO) and Comments for both draft solicitations due by 25 February 2021 »  Details.
16 December 2020
The 237th Meeting of the American Astronomical Society, Virtually Anywhere, 11–15 January 2021, will include Physics of the Cosmos events. The PCOS AAS2021 Meeting page lists currently scheduled sessions, presentations, chats, and displays »  Details.
4 December 2020
Payloads and Research Investigations on the Surface of the Moon (PRISM) Step-2 Due Date. Step-2 proposals now due 3 February 2021. Step-1 proposal due date unchanged as 11 December 2020 »  Details.
4 December 2020
Release of Final text and Due Dates for ROSES Post-COVID Recovery program. Requests received by 4 January 2021 will be processed first. Final due date is 5 March 2021. »  Details.

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