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News from the center of our galaxy.

News from the center of our galaxy

Astronomers and astrophysicists argue over what lies in thecenter of our Milky Way galaxy. They know that something that produces a lot of energy is there. Is it a black hole? Or a cluster of highly active stars? Or something else?

We can't see the center of our galaxy; it is obscured by darkclouds of dust. Our information comes from radio and, particularly, infrared observations, which generally have poor resolution, making it difficult to locate and separate small objects. Once every 18 years, lunar occultation gives observers an opportunity to sharpen the resolution. According to Eric E. Becklin of the University of Hawaii at Manoa, the first analyses of such an observing run, done last September, show in the galactic center a compact, bright infrared object, which astrophysicists do not yet know how to fit into their picture of the area.

The moon's motions in the sky follow an 18-year cycle calledthe Saros. Once during each 18-year period comes a series of months when the moon passes, once each month, through the constellation Sagittarius, and so between us and the center of the galaxy. That time is now, and in this cycle there will be eight opportunities to watch the moon occult, or pass in front of, the center of our galaxy, Becklin says.

As a result of millennia of observations, astronomers knowvery precisely where the moon is in the sky at any instant. The moon, lacking an atmosphere, has a very sharp edge. Thus, as it progressively cuts off radiation coming from behind it, astronomers can tell precisely the direction that radiation was coming from.

The September occultation, which is still being analyzed, revealeda compact object that astrophysicists had not been aware of. It's one of the warmer sources, Becklin says, being bright in the near infrared. It's compact, not a star, and almost too compact to be a cluster of stars. A group led by Charles Townes of the University of California at Berkeley speculates that the object has a large mass, which is typical of a black hole. Still, Becklin says, observers don't want to say at this point that there's a black hole there.
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Title Annotation:galactic center observed during lunar occultation
Author:Thomsen, Dietrick E.
Publication:Science News
Date:Jan 10, 1987
Words:365
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