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In this issue:
Shedding Light on a Cosmic Mystery
Science Today: GLAST's Dance Card Begins to Fill
Panofsky on Physics, Politics and Peace--Pief Remembers Released Today
Mark Your Calendars: October 11th All-Hands Briefing
Thursday - October 4, 2007
Shedding Light on a Cosmic Mystery
A SLAC astrophysicist and his collaborators may have finally solved the long-standing conundrum about the origin of cosmic rays. These streams of subatomic particles—mostly protons—continuously careen through our galaxy, bombarding Earth's atmosphere with tremendous energies. Since their discovery in 1912, researchers have marveled at how ordinary particles could attain such extraordinary energies, but despite intense experimental and theoretical efforts, these questions have eluded definitive answers.
The predominant theory has posited that cosmic rays are accelerated in the supersonic shocks surrounding supernova remnants. According to this hypothesis, turbulent magnetic fields force the particles to ricochet wildly across the shockfront, gaining energy with every crossing until eventually releasing into the cosmos at relativistic speeds. Until now, however, most evidence for this conjecture was circumstantial, relying on theory and logic rather than direct observation.
Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) post-doc Takaaki Tanaka and colleagues have found definitive evidence that supernova remnants are accelerators of cosmic rays, reporting their results in the October 4 issue of Nature. Read more...
GLAST's Dance Card Begins to Fill
The Gamma-ray Large Area Space Telescope (GLAST) is scheduled for launch early next year, and although it will observe a great variety of interesting high-energy sources, one type of object in particular is expected to dominate the gamma-ray sky: a special class of active galactic nuclei known as "blazars." GLAST will detect thousands of blazars, and in anticipation of this volume of new data, Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) astronomers, in collaboration with their colleagues at Caltech, at Oxford, and in Europe, have assembled the Candidate Gamma-Ray Blazar Survey, or CGRaBS.
The goal of the CGRaBS project is to select, in advance of the launch of GLAST, the best and brightest sources that GLAST will see. CGRaBS has identified the 1,625 objects that have radio and X-ray properties that are the most "blazar-like." The CGRaBS team attempts to gather optical data on each source to determine its precise classification and its redshift, which is a measure of its distance from us. Most of the CGRaBS optical campaign has been conducted on the Hobby-Eberly Telescope at McDonald Observatory in west Texas. Additional observations have been conducted at other large telescopes throughout the world, including at Palomar Observatory in southern California, at the Very Large Telescope in Chile, and at the 10-meter Keck telescope at the summit of Mauna Kea.
By learning about as many objects as possible before GLAST launches, the CGRaBS team can pick out the most interesting or unusual sources in advance, allowing them to identify which sources will warrant more careful study in the GLAST era. In essence, by "doing their homework" on these objects before GLAST detects them, the team can avoid constantly having to "play catch-up" after GLAST detects them. With the CGRaBS list as a guide, and the unprecedented quality of the gamma-ray data from GLAST, the coming years will be a very exciting time for blazar science.
Panofsky on Physics, Politics and Peace—Pief Remembers
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