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microwave emissions
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The Cosmic Microwave
Background
A microwave is a comparatively
short electromagnetic wave that lies between the 1 meter and 1
millimeter wavelengths within the electromagnetic spectrum (see
graph below). In our case, the cosmic microwave background is the
faint but pervasive glow of radiation that remains from the
primordial fireball that gave birth to the universe. This
microwave background radiation provides a picture of what the
universe was like some 300,000 years after the Big Bang.
In 1992, NASA's Cosmic Background
Explorer (COBE) satellite detected slight variations in the
cosmic microwave background. One goal of the project was to map
the intricate structure of the interstellar medium, the gas and
dust between the stars that is the site of new star formation.
Illuminated by stellar ultraviolet light or heated by shock
waves, the interstellar gas shows a structure of arcs and
bubbles. These tiny ripples in radiation correspond to density
fluctuations in the early universe, which coalesced into the
galaxies and superclusters of galaxies that we see today.
By mapping the sky in
hydrogen-alpha light, the survey will provide a template for
subtracting Galactic emissions from the cosmic microwave
background. Astronomers in South America have recently been
imaging the southern heavens in hydrogen-alpha light every night
thanks to a new robotic telescope installed at Cerro Tololo
Inter-American Observatory in Chile the tedium of sky mapping is
handled autonomously. This new sky survey could be used to
decontaminate the existing COBE measurements, as well as those of
future satellites, such as the Microwave Anisotropy Probe,
scheduled for launch in two years.
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