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Chandra X-Ray Camera Turned On: A Report from Professor Gordon Garmire of Penn State, the Principal Investigator for the Chandra Observatory's ACIS X-ray Camera

27 July 1999

NOTE: The following is the first in a series of dispatches from Gordon Garmire, the Evan Pugh Professor of Astronomy and Astrophysics and principal investigator of the team that conceived and designed the ACIS X-ray camera -- used for viewing high-energy objects in the farthest reaches of the universe.  The camera is part of the Chandra X-Ray Observatory, which was launched on the space shuttle Columbia on 23 July 1999.

ACIS, the primary X-ray Camera of the Chandra Observatory was turned on last night to check its calibrations and to verify that it survived the launch on the Space Shuttle Columbia.  ACIS will be used to take X-ray pictures of the universe.  The data look fantastic and we are really excited about opening the mirror covers next week to begin taking X-ray images of the 'hot' universe.

We are eager to begin observing the center of our Milky Way Galaxy, where a massive black hole has been suspected to exist.  It is something of a mystery why this black hole, which is thought to contain the mass of two million Suns, has not been seen to emit X-rays, while other black holes of a mere ten solar masses in the neighborhood of our solar system emit a billion times as much X-ray energy as our Sun.  One possibility is that the Galactic Center black hole is 'starved,' that is to say there is very little matter close to the black hole for it to attract into its powerful gravitational grip.  It is this 'swallowing' of matter that causes the black hole to become visible to us in X-rays--the matter becomes very hot, nearly a billion degrees, as it is pulled into the immense gravitational field of the black hole.  The puzzle is that the gas near the galactic center is thought to be quite dense and should be providing enough material to 'feed' the black hole and make it 'shine' brightly in X-rays.

We will use ACIS to peer nearly one hundred times deeper than previously possible to search for the answer to the mystery of the missing X-rays.


To reach Gordon Garmire on Wednesday or Thursday: Barbara K. Kennedy (PIO): 814-863-4682,

Gordon Garmire beginning on Friday (30 July 1999): 814-865-1117,