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Galactic center: a bunch of IR sources.

Galactic center: A bunch of IR sources

Astronomers like to observe an object in as many different wavelengths of radiation as they can. Usually each different range of the spectrum contributes its own piece of information to an overall picture of whatever the object is. Sometimes, however, such a multiplicity of observations engenders confusion rather than mutual support. Such is the case with some recent infrared (IR) observations of the center of our galaxy.

Surrounded by dust clouds, the galactic center is virtually impossible to see in visible light. So it was not until recent years that radio and X-ray observations found evidence of highly energetic processes going on there. In the last couple of years certain radio astronomers, finding evidence of a single very bright object, concluded that a large black hole could be at the center of that object, supplying the push for the activities that produce such strong radio waves.

However, the infrared observations in question, by William Forrest and Judith Pipher of the University of Rochester (N.Y.) and Wayne Stein of the University of California at San Diego, show a jumble of sources, none of which seems bright enough to represent the immediate surroundings of such a large black hole. Therefore, says Forrest, "the subject is still being debated.'

The photo shown here is one of the first attempts to make an infrared picture of an area of sky in the same way an optical telescope does, rather than scanning back and forth across the area with a single infrared sensor. The instrument used for the imaging is an array of indium antimonide elements, each of which serves as a "pixel' sensing a piece of the total picture and converting the infrared brightness it records into an electrical signal that it dumps into a computer memory.

A source, which these observers designate IRS 16NW--just below IRS 7 in the photo--is unusual enough, however, to deserve a further look to see whether it could relate to some of the things seen in radio and X-ray. In addition, the new imaging method also permits infrared spectroscopy, the study of emissions by particular substances or physical processes in the source. Forrest and coworkers plan observations of these kinds in the near future and expect that they will contribute significantly to the astrophysical discussion.
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Author:Thomsen, D.E.
Publication:Science News
Date:Nov 9, 1985
Words:385
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