ACIS image of the zone of avoidance
Credit: NASA/GSFC/K. Ebisawa et al.

In the Zone of Avoidance

Astronomers making a map of the distribution of galaxies on the sky noticed a peculiar thing - there seemed to be a narrow band on the sky in which very few galaxies were found. This band was named the "zone of avoidance" since galaxies seemed to avoid this region of the sky. We realize that this zone of avoidance is produced by the large clouds of gas and dust in the Milky Way. Since the Milky Way is a spiral galaxy, most of the gas and dust lies along the plane of the Milky Way, and thus these clouds block out light from distant galaxies if they happen to lie in the band of the Milky Way. But high energy X-rays can penetrate through large amounts of gas and dust, giving astronomers the chance to finally see what lies in the zone of avoidance. The image above is the first image of the high-energy X-ray emission from a region of the zone of avoidance in the constellation of Scutum. This image, obtained by astronomers using the Chandra X-ray observatory, is color-coded to show the energy of the emitted X-rays. The pink and red objects are objects which produce relatively low-energy emission and are probably nearby stars in the Milky Way, while the blue objects emit high-energy X-rays and are probably distant galaxies. Astronomers also see a "blue glow" produced by high-temperature clouds of gas in the Milky Way. This hot gas (at temperatures of many millions of degrees) probably was produced by ancient supernovae in the Milky Way.

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Page Author: Dr. Michael F. Corcoran
Last modified December 10, 2001