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COBE maps the interstellar medium.


An unprecedented, panoramic survey of the Milky Way at microwave and far-infrared wavelengths has yielded new insights into the heating and cooling processes that drive starbirth in our galaxy Astronomers created the galactic map using a detector aboard the Cosmic Background Explorer (COBE) spacecraft (SN: 11/10/90, p.301).

The detector, called the Far-infrared Absolute Spectrophotometer, recorded the location and intensity of interstellar ionized nitrogen at a wavelength of 205 microns, providing the first measurements ever of this spectral line. Researchers from NASA's Goddard Space Flight Center in Greenbelt, Md., and the University of California, Los Angeles, described the survey results at this week's meeting of the American Astronomical Society in Philadelphia.

The intensity of the radiation indicates that ionized nitrogen may be three times as abundant as expected, suggesting that the energy-absorbing ions play a key role in cooling interstellar gas, reports Charles L. Bennett of Goddard. He adds that measurements of another nitrogen emission line indicate a relatively low ionic density, equivalent to five ions in a cubic-inch box.

The strength and pervasiveness of the 205-micron emission supports the notion that "warm" regions of gas and dust lie between the cold, collapsing cores of starbirth clouds and the clouds' outer layers of hot gas, Bennett says. In addition, says David J. Hollenbach of NASA's Ames Research Center in Mountain View, Calif., it suggests that our galaxy forms stars more rapidly than predicted.

The COBE detector also measured the total luminosity of galactic dust and recorded the far-infrared emissions from neutral carbon atoms and carbon monoxide in the interstellar gas. In comparing these measurements with those for 20 other spiral galaxies, COBE investigators conclude that the Milky Way behaves like a typical spiral galaxy.
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Title Annotation:Cosmic Background Explorer
Author:Cowen, Ron
Publication:Science News
Date:Jan 19, 1991
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