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Briefing Materials: NASA'S Fermi Measures Cosmic 'Fog' Produced by Ancient Starlight
11.01.12
 
NASA is holding a media teleconference at 2 p.m. EDT on Thursday, Nov. 1, 2012, to discuss new measurements using gamma rays to investigate ancient starlight with the Fermi Gamma-ray Space Telescope.

Audio of the teleconference is being streamed live on NASA's website at:

http://www.nasa.gov/newsaudio

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Briefing Speakers

  • Justin Finke, astrophysicist, Naval Research Laboratory, Washington, D.C.
  • Marco Ajello, astrophysicist, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, and the Space Sciences Laboratory, University of California at Berkeley
  • Volker Bromm, associate professor, department of astronomy, University of Texas at Austin


Images and Multimedia in Support of the News Conference


Presenter 1: Justin Finke, astrophysicist, Naval Research Laboratory, Washington, D.C.

Visual 1: Blazars are active galaxies powered by supermassive black holes. Some of the matter falling toward the black hole is accelerated to near the speed of light and blasted outward in a pair of oppositely directed jets. Blazars are bright sources because one of these jets happens to be pointing directly toward us. (Credit: NASA's Goddard Space Flight Center/Conceptual Image Lab)
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graphic depicting extragalactic background light Visual 2: Ultraviolet and visible light emitted by all the stars that ever existed is still coursing through the universe. Astronomers refer to this "fog" of starlight as the extragalactic background light (EBL). Credit: NASA's Goddard Space Flight Center
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graphical depiction of gamma rays interact with the extragalactic background light Visual 3: Gamma rays interact with the EBL, which gives astronomers a means to probe the stellar content of the cosmos. When a gamma ray (magenta) strikes ultraviolet or visible light (blue), the photons are transformed into an electron and its antimatter counterpart, a positron. This process removes gamma rays from the spectra of bright sources like blazars. The degree of absorption increases for sources at greater distances Credit: NASA's Goddard Space Flight Center
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Presenter 2: Marco Ajello, astrophysicist, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, and the Space Sciences Laboratory, University of California at Berkeley

Visual 1: This animation tracks several gamma rays through space and time, from their emission in the jet of a distant blazar to their arrival in Fermi's Large Area Telescope (LAT). During their journey, the number of randomly moving ultraviolet and optical photons (blue) increases as more and more stars are born in the universe. Eventually, one of the gamma rays encounters a photon of starlight and the gamma ray transforms into an electron and a positron. The remaining gamma-ray photons arrive at Fermi, interact with tungsten plates in the LAT, and produce the electrons and positrons whose paths through the detector allows astronomers to backtrack the gamma rays to their source. (Credit: NASA's Goddard Space Flight Center/Cruz deWilde)
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This plot shows the locations of 150 blazars (green dots) used in the EBL study. Visual 2: This plot shows the locations of 150 blazars (green dots) used in the EBL study. The background map shows the entire sky and was constructed from four years of gamma rays with energies above 10 billion electron volts (GeV) detected by Fermi. The plane of our Milky Way galaxy runs along the middle of the plot. The Fermi LAT instrument is the first to detect more than 500 sources in this energy range. Credit: NASA/DOE/Fermi LAT Collaboration
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lighthouse in fog Visual 3: A foggy day at Duncansby Head Lighthouse on the northeastern tip of the Scottish mainland provides a useful analogy for the EBL measurements. The lighthouse is the blazar's gamma-ray emission, which must travel through the cosmic "fog" of starlight (photons of ultraviolet and visible light) before it reaches Fermi. Credit: Wikimedia Commons image © user Akinom, CC-BY-SA-3.0
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Fermi measured the amount of gamma-ray absorption in blazar spectra produced by ultraviolet and visible starlight at three different epochs in the history of the universe. Visual 4: Fermi measured the amount of gamma-ray absorption in blazar spectra produced by ultraviolet and visible starlight at three different epochs in the history of the universe. Credit: NASA's Goddard Space Flight Center
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This illustration places the Fermi measurements in perspective with other well-known features of cosmic history. Visual 5: This illustration places the Fermi measurements in perspective with other well-known features of cosmic history. Star formation reached a peak when the universe was about 3 billion years old and has been declining ever since. Credit: NASA's Goddard Space Flight Center
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depiction of potential number of stars per 100 billion cubic light-years Visual 6: The Fermi EBL measurements allow astronomers to constrain the number of stars that have ever shone in the universe. Moving forward, the measurements will serve as a guide for theoretical studies of the early universe, near the peak of star formation. Credit: NASA's Goddard Space Flight Center
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Presenter 3: Volker Bromm, associate professor, department of astronomy, University of Texas at Austin

No visuals.