Mysterious Objects at the Edge of the Electromagnetic Spectrum   
       
   March 16, 2012:  The human eye is crucial to astronomy. Without the ability to   
   see, the luminous universe of stars, planets and galaxies would be closed to   
   us, unknown forever. Nevertheless, astronomers cannot shake their fascination   
   with the invisible.   
       
   Outside the realm of human vision is an entire electromagnetic spectrum of   
   wonders. Each type of light---from radio waves to gamma-rays--reveals   
   something unique about the universe. Some wavelengths are best for studying   
   black holes; others reveal newborn stars and planets; while others illuminate   
   the earliest years of cosmic history.   
       
   NASA has many telescopes "working the wavelengths" up and down the   
   electromagnetic spectrum. One of them, the Fermi Gamma-Ray Telescope orbiting   
   Earth, has just crossed a new electromagnetic frontier.   
       
   A new ScienceCast video takes viewers on a trip to the edge of the   
   electromagnetic spectrum, where mysterious objects are puzzling astronomers.     
   "Fermi is picking up crazy-energetic photons," says Dave Thompson, an   
   astrophysicist at NASA's Goddard Space Flight Center. "And it's detecting so   
   many of them we've been able to produce the first all-sky map of the very high   
   energy universe."   
       
   "This is what the sky looks like near the very edge of the electromagnetic   
   spectrum, between 10 billion and 100 billion electron volts."   
       
   The light we see with human eyes consists of photons with energies in the   
   range 2 to 3 electron volts. The gamma-rays Fermi detects are billions of   
   times more energetic, from 20 million to more than 300 billion electron volts.   
   These gamma-ray photons are so energetic, they cannot be guided by the mirrors   
   and lenses found in ordinary telescopes. Instead Fermi uses a sensor that is   
   more like a Geiger counter than a telescope. If we could wear Fermi's gamma   
   ray "glasses," we'd witness powerful bullets of energy - individual gamma rays   
   - from cosmic phenomena such as supermassive black holes and hypernova   
   explosions. The sky would be a frenzy of activity.   
       
   Before Fermi was launched in June 2008, there were only four known celestial   
   sources of photons in this energy range. "In 3 years Fermi has found almost   
   500 more," says Thompson.   
       
   What lies within this new realm?   
       
   "Mystery, for one thing," says Thompson. "About a third of the new sources   
   can't be clearly linked to any of the known types of objects that produce   
   gamma rays. We have no idea what they are."   
       
   The rest have one thing in common: prodigious energy.   
       
   An artist's concept of giant 'Fermi bubbles' emerging from the heart of the   
   Milky Way. [more] "Among them are super massive black holes called blazars;   
   the seething remnants of supernova explosions; and rapidly rotating neutron   
   stars called pulsars."   
       
   And some of the gamma rays seem to come from the 'Fermi bubbles' - giant   
   structures emanating from the Milky Way's center and spanning some 20,000   
   light years above and below the galactic plane.   
       
   Exactly how these bubbles formed is another mystery.   
       
   Now that the first sky map is complete, Fermi is working on another, more   
   sensitive and detailed survey.   
       
   "In the next few years, Fermi should reveal something new about all of these   
   phenomena, what makes them tick, and why they generate such 'unearthly' levels   
   of energy," says David Paneque, a leader in this work from the Max Planck   
   Institute in Germany.   
       
   For now, though, there are more unknowns than knowns about "Fermi's world."   
       
   Says Thompson: "It's pretty exciting!"   
       
       
   Authors: Dauna Coulter, Dr. Tony Phillips  |  Credit: Science@NASA   
       
   More Information   
   NASA's Fermi Space Telescope Explores New Energy Extremes -- press release   
       
   The Fermi Gamma-ray Space Telescope -- home page   
       
   Credits: NASA's Fermi Gamma-Ray Space Telescope mission is an astrophysics and   
   particle physics partnership, developed in collaboration with the U.S.   
   Department of Energy, along with important contributions from academic   
   institutions and partners in France, Germany, Italy, Japan, Sweden, and the   
   United States. The mission's main instrument, the Large Area Telescope (LAT),   
   is making pioneering observations of gamma-ray bursts at higher energies than   
   ever before from space. Another instrument onboard, the Fermi Gamma-Ray Burst   
   Monitor, is monitoring gamma-ray bursts at lower energies. The combination of   
   the GBM and the LAT provides a powerful tool for studying GRBs over a very   
   wide range of energies. The GBM is a collaboration among scientists at the   
   Marshall Space Flight Center, the University of Alabama in Huntsville, the Max   
   Planck Institute for Extraterrestrial Physics in Germany, and the Los Alamos   
   National Laboratory.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.78   
    * Origin: NCS BBS (1:3828/7)