Astroparticle Physics Italian Style

Gamma rays are the most energetic form of radiation, and they can signal powerful sources in the cosmos. Yet the gamma-ray sky is still relatively poorly understood. In a plenary talk, Julie McEnery, from NASA’s Goddard Space Flight Center in Greenbelt and the University of Maryland in College Park, outlined what scientists have learned from almost a decade of gamma-ray observations with NASA’s Fermi space observatory and the Italian space agency’s AGILE telescope. These instruments have allowed researchers to discover new gamma-ray sources, and have advanced our understanding of pulsars, gas nebulae and gamma-ray bursts.

Giving a striking example, McEnery said that observations have forced a rethink of the particle-acceleration mechanisms that take place in the nebula contained within the Crab supernova remnant (pictured above). The Crab is the shattered remains of a star that exploded nearly 1000 years ago. At its center lies a magnetized neutron star spinning 30 times a second. In 2010 and 2011, Fermi and AGILE detected several surprising short-lived outbursts of gamma rays from the nebula at energies greater than 100 million electron volts. One such superflare was about 30-fold more energetic than the nebula's typical gamma-ray output. On the basis of the observed gamma-ray emission, researchers estimate that these events are caused by electrons accelerated to energies of more than a million billion electron volts—huge energies, even for astrophysical sources. McEnery said that models of how particles get their energy in the Crab have been “blown out of the water” by these new observations, which have prompted a re-examination of what might be going on in this historic object.

In a session dedicated to outreach projects, multimedia developer João Pequenão from the CERN Media Lab, near Geneva, Switzerland, delivered an account of the making of a new planetarium show titled “Phantom of the Universe: The Hunt for Dark Matter.” The 25-minute film will take viewers on a journey through space and time that begins with the big bang and ends at CERN’s Large Hadron Collider (LHC). It tells the fascinating story of how dark matter was discovered and researchers’ ongoing efforts to find what it is made of. And it describes the three main channels of research on dark matter: astrophysics, particle-collider experiments such as the LHC, and experiments conducted using detectors buried deep underground such as the Large Underground Xenon detector in South Dakota.

Pequenão said the film will be the first time that the field of high-energy physics is highly featured in a planetarium show. He and the movie's creator Michael Barnett from the Lawrence Berkeley National Laboratory, brought together an eclectic and international mix of professionals, including the 2006 physics Nobel Prize laureate George Smoot, musicologist Mickey Hart, award-winning, Hollywood-based filmmaker Carey Ann Strelecki, and several other artists. The film is currently in the final stages of production, and will be ready for free screenings across the world around the end of the year. It will initially be available in full-dome format and later possibly also in flat-screen and IMAX formats. In the meantime, a full draft, snapshots, and a trailer of the film can be seen at http://phantomoftheuniverse.com/. Enjoy!