Paula Cleggett-Haleim
  Headquarters, Washington, D.C.                   January 14, 1991
  (Phone:  202/453-1549)                           Noon
  
  Randee Exler
  Goddard Space Flight Center, Md.
  (Phone:  301/286-7277)
  
  
  RELEASE:  91-6
  
  COBE MAPS INTERSTELLAR MATERIAL IN MILKY WAY GALAXY
  
  
       For the first time, astronomers have mapped the distribution 
  of nitrogen throughout our galaxy.  The new observations were 
  taken by an instrument on NASA's Cosmic Background Explorer, the 
  Far Infrared Absolute Spectrophotometer.
  
       This all-sky survey, along with additional maps of carbon 
  and dust, provides quantitative information that may enable 
  scientists to understand better the heating and cooling processes 
  that take place throughout the Milky Way.  These accomplishments 
  were reported today at the American Astronomical Society meeting 
  in Philadelphia by members of the COBE science team.
  
       COBE scientists presented images that show the locations in 
  the galaxy of ionized nitrogen.  The nitrogen map of the Milky 
  Way is at the wavelength of 205 micrometers and is the first 
  detection of this important spectral line.  The carbon map was 
  produced at 158 micrometers and the dust map at 205 micrometer 
  wavelengths.
  
       "Before COBE, it was not possible to map the whole galaxy in 
  this way, although these atomic emissions are the dominant way in 
  which the interstellar gas cools," said COBE Project Scientist 
  Dr. John C. Mather, who added that COBE's unique capabilities 
  permit these all-sky measurements unencumbered by atmospheric and 
  instrument emission.  Five months of data were used to produce 
  the maps.
  
  
  
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       The emission from ionized nitrogen atoms was found to occur 
  at a precise wavelength of 205.3 micrometers.  The exact 
  determination of this wavelength, which had never been measured 
  before, is important because it will enable astronomers to build 
  future instruments to map this radiation with greater spatial 
  resolution.
  
       The COBE data also were used to measure the total energy 
  emitted by the dust, neutral carbon atoms and carbon monoxide 
  molecules in the interstellar gas, showing that our galaxy is a 
  typical spiral galaxy.
  
       These new data show that carbon and nitrogen atoms -- some 
  of the key building blocks of life -- are extremely widespread in 
  the thin gas that fills the space between the stars.  These atoms 
  are created inside stars by nuclear reactions and then released 
  back into space by stellar winds or explosions at the ends of 
  stellar lives.
  
       The data also confirm theories that the mixture of gas and 
  dust in our galaxy is heated by starlight striking dust grains 
  and cooled by the carbon and nitrogen emissions.  The greatest 
  concentrations of the atoms and dust grains are in the plane of 
  the galaxy.
  
       The data were taken using the Far Infrared Absolute 
  Spectrophotometer (FIRAS), one of the three instruments aboard 
  COBE, NASA's first satellite primarily designed for cosmological 
  studies.  COBE, launched from Vandenberg Air Force Base, Calif., 
  Nov. 18, 1989, primarily studies the diffuse microwave and 
  infrared light coming from the "big bang" at the beginning of the 
  currently observable universe and from the first objects that 
  formed after this primordial explosion.
  
       FIRAS is the same instrument that 1 year ago enabled COBE 
  scientists to report the most precise measurements ever obtained 
  of the spectrum of the cosmic microwave background radiation.  
  The new results show that this instrument also is remarkably 
  sensitive to emissions of dust grains, atoms and molecules in the 
  galaxy.
  
       The report was made by Drs. John C. Mather, Richard A. 
  Shafer and Charles L. Bennett of NASA's Goddard Space Flight 
  Center, Greenbelt, Md., and Dr. Edward L. Wright, of the 
  University of California.
  
  
  
  
  
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       The data were analyzed at the Goddard Space Flight Center. 
  The scientific team includes members at Massachusetts Institute 
  of Technology, Cambridge, Mass.; General Research Corp., Danvers, 
  Mass.; Princeton University, N.J.; University of California at 
  Los Angeles, and the Jet Propulsion Laboratory, Pasadena, Calif., 
  as well as the Goddard Space Flight Center.  Scientists at 
  General Sciences Corp., Laurel, Md., Applied Research Corp., 
  Landover, Md.; Universities Space Research Association, 
  Greenbelt, Md., and Systems Technologies Corp., Lanham, Md., 
  support the reduction and analysis of the data.
  
       This research is supported by NASA's Astrophysics Division 
  of the Office of Space Science and Applications.
  
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