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History of X-Ray Astronomy
The most important X-ray astronomy
mission of the present decade is NASA's Chandra X-ray Observatory, which was
launched on July 23, 1999. This telescope contains four sets of nested mirrors
and is the premier X-ray observatory to date. It can detect sources more than
twice as far away and produce images with five times greater detail. The mirrors
have been polished to a smoothness of a few atoms. If the surface of the Earth
were as smooth as the Chandra mirrors, the largest mountain would be less than 2
meters (7 feet) tall!
X-ray telescopes have a different design from optical telescopes because X-rays
will reflect off mirrors only if they strike them at grazing angles. Two
reflections are used to focus the X-rays to a point.
The area of an X-ray telescope can be increased by nesting the mirrors inside
one another.
The largest of eight mirrors for Chandra is shown at the Eastman-Kodak
laboratory, where the circular support structure was built. The mirror surface
was coated with iridium, a material more reflective than gold.
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