[escepticos] First Observation of Space-Time Distortion By Black Holes

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Donald Savage
Headquarters, Washington, DC                   November 6, 1997
(Phone:  202/358-1547)

Bill Steigerwald
Goddard Space Flight Center, Greenbelt, MD
(Phone:  301/286-5017)

RELEASE:  97-258

FIRST OBSERVATION OF SPACE-TIME DISTORTION BY BLACK HOLES

       Astronomers using NASA's Rossi X-ray Timing Explorer (RXTE) 
spacecraft reported today that they have observed a black hole 
that is literally dragging space and time around itself as it 
rotates.  This bizarre effect, called "frame dragging," is the 
first evidence to support a prediction made in 1918 using 
Einstein's theory of relativity.  

       The phenomenon is distorting the orbit of hot, X-ray 
emitting gas near the black hole, causing the X-rays to peak at 
periods that match the frame-dragging predictions of general 
relativity.  The research team, led by Dr. Wei Cui of the 
Massachusetts Institute of Technology, is announcing its results 
in a press conference today during the American Astronomical 
Society's High Energy Astrophysics Division (HEAD) meeting in 
Estes Park, CO.  Collaborators in the research include Dr. Wan 
Chen of NASA's Goddard Space Flight Center, Greenbelt, MD, and Dr. 
Shuang N. Zhang of NASA's Marshall Space Flight Center, 
Huntsville, AL. 

       "If our interpretation is correct, it could demonstrate the 
presence of frame dragging near spinning black holes," said Cui.  
"This observation is unique because Einstein's theory has never 
been tested in this way before."

       Black holes are very massive objects with gravitational 
fields so intense that near them, nothing, not even light, can 
escape their pull.  This effect shrouds the hole in darkness, and 
its presence can only be inferred from its effects on nearby 
matter.  Many of the known or suspected black holes are orbiting a 
close "companion" star.  The black hole's gravity pulls matter 
from the companion star, which forms a disk around the black hole 
as it is drawn inward by the black hole's gravity, much like soap 
suds swirling around a bathtub drain.  Gas in this disk gets 
compressed and heated and emits radiation of various kinds, 
especially X-rays. 

       The research team used these X-ray emissions to determine 
if frame dragging was present.  The team found that the X-ray 
emissions were varying in intensity.  By analyzing this variation, 
they found a pattern, or repetition, that was best explained by a 
perturbation in the matter's orbit.  This perturbation, called a 
precession, occurs when the orbit itself shifts around the black 
hole.  This is evidence for frame dragging because as the matter 
orbits the black hole, the space-time that is being dragged around 
the black hole drags the matter along with it.  This shifts the 
matter's orbit with each revolution.

       Einstein's Theory of General Relativity has been highly 
successful at explaining how matter and light behaves in strong 
gravitational fields, and has been successfully tested using a 
wide variety of astrophysical observations.  The frame-dragging 
effect was first predicted using general relativity by Austrian 
physicists Joseph Lense and Hans Thirring in 1918.  Known as the 
Lense-Thirring effect, it has not been definitively observed thus 
far, so scientists will scrutinize the new reports very carefully.

       The possible detection of frame dragging around another 
type of very dense, quickly spinning objects, called neutron 
stars, was accomplished very recently by Italian astronomers, 
whose work led Dr. Cui's team to seek the effect near black holes.  
The Italians, Drs. Luigi Stella of the Astronomical Observatory of 
Rome, and Mario Vietri of the Third University of Rome, will 
report their findings at the November 6 conference in Estes Park.  
These observations also were made using the RXTE, which is 
available for use by astronomers throughout the world. 

       "This is exciting work that needs further confirmation, as 
for any seemingly major advance in science," said Dr. Alan Bunner, 
Director of the Structure and Evolution of the Universe Program at 
NASA Headquarters, Washington, DC.

       The RXTE spacecraft is a 6,700 pound observatory placed 
into orbit by NASA in December 1995.  Its mission is to make 
astronomical observations from high-energy light in the X-ray 
range, which is emitted by powerful events in the universe.  These 
events are often associated with massive, compact objects such as 
black holes and neutron stars.  

                         - end -

NOTE TO EDITORS:  Computer animation and background video to 
illustrate this story is available and will be broadcast on NASA 
TV Videofile Nov. 6.