MILKY WAY GALAXY looks profoundly different depending on the frequency at which astronomers observe it. Fifty years ago, when astronomers were restricted to visible light, interstellar gas seemed like just a nuisance--blocking the real objects of interest, the stars. Today scientists think the gas may be as important to the evolution of the galaxy as are the stars.

These panels appear on a poster prepared by the NASA Goddard Space Flight Center; for more information, visit http://nvo.gsfc.nasa.gov/mw/mmw_sci.html

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