In DepthAstrophysics

Catching cosmic rays where they live

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Science  07 Aug 2015:
Vol. 349, Issue 6248, pp. 572-573
DOI: 10.1126/science.349.6248.572

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The International Space Station (ISS) is broadening its role as a cosmic ray observatory. Two new instruments are slated to join the massive Alpha Magnetic Spectrometer (AMS) in detecting high-energy particles from space outside Earth's distorting atmosphere. High-energy cosmic rays give scientists unique glimpses into their sources, thought to include exotic objects such as supernovae. The new experiments—the CALorimetric Electron Telescope (CALET), and Cosmic Ray Energetics and Mass for the International Space Station (ISS-CREAM, pronounced "ice cream")—will measure cosmic rays at energies many times higher than AMS can reach, at a fraction of its $1.5 billion price tag. Unlike the wide-ranging AMS, each will stick to a narrow roster of particles and energies. CALET, scheduled for launch this month, will set its sights on high-energy electrons, which could shed light on relatively nearby supernova remnants and possibly on clumps of dark matter. ISS-CREAM, slated for launch in June 2016, will study high-energy atomic nuclei from hydrogen up through iron for clues to what drives supernova explosions. Another ISS detector, the Extreme Universe Space Observatory at the Japanese Module (JEM-EUSO)—under consideration for launch in 2021—would point a wide-angle ultraviolet camera toward Earth, watching for showers of particles that ultrahigh-energy cosmic rays spawn when they hit the atmosphere.