Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, January 13, 1994 TAG: 9401130046
SECTION: NATL/INTL PAGE: A4 EDITION: METRO
SOURCE: Associated Press
DATELINE: ARLINGTON LENGTH: Medium
Astronomers who have gotten reports on the work indicated at a national meeting of the American Astronomical Society that the Hubble's vision is fixed.
The Hubble will be able to provide final proof of the existence of black holes by measuring how fast stars are being pulled into the center of galaxies by immense gravitational force, said Gary Bower of the Space Telescope Institute.
"The search for black holes is a top priority for the Hubble Space Telescope, and our efforts have been frustrated" by the blurred image, said Bower.
Asked if the repair corrected the telescope's view sufficiently to prove the existence of black holes, Bower said, "Yes, it will."
"The checkout has gone far better than anyone had hoped," said an astronomer connected with the program. He asked not to be identified, but said that "everything has been done right on time in the tests." Repairs were done during the December space shuttle mission.
The National Aeronautics and Space Administration is to formally announce today whether the fix-it job was successful.
A black hole is thought to be an ancient star, at least three times the size of the sun, that has collapsed into a single point only a few miles across. Matter is so dense that it creates a powerful gravitational force that draws everything nearby, including stars, into its center. Gravity becomes so intense in a black hole that nothing escapes, including light. Hence, the object is dark and cannot be viewed directly.
Instead, astronomers measure the movement of objects and gas nearby and determine from their velocity the power of the gravitational point.
Bower said that based on measurements made by the Hubble before its repair and by ground-based telescopes, astronomers have found about 20 galaxies that may have black holes at their center. But no final proof has been found.
The problem, he said, is that instruments, including the defective Hubble, have not been able to measure velocities of stars as they approach the cusp of a black hole. As matter moves faster and faster, it heats up and releases bursts of light and radiation that blot out the view. As a result, earlier instruments could not observe stars in their final dash to oblivion.
Bower said the repaired Hubble will provide that capability.
Proof of a black hole will come if stars near the galactic center are found to be moving at about 250,000 miles an hour. If stars move more slowly in that region, said Bower, it would be evidence of no black hole.
by CNB