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A Dent in the Space-Time Fabric?
What does a dent in the “fabric” of space and time look like? The cause in a faraway place is invisible, scientists say. But theorists believe its existence can be deduced from certain repetitive events.
In January this year scientists reported that in 2005 two unusual X-ray frequencies were detected coming from an extremely energetic light source, GRO J1655-40. The source is seen in the constellation Scorpius and it is estimated to lie about 10,000 light-years from Earth. Astronomers say it is a “stellar black hole” about seven times the mass of our Sun, gradually consuming the matter of a companion star.
The emissions seemed strange because scientists had recorded identical emissions nine years earlier—an improbable coincidence, they thought. This got them to thinking, and the chain of reasoning that followed led to a report given at a recent meeting of the American Astronomical Society.
The centerpiece of the story is a black hole, and black holes are said to form in the death throes of massive stars as their fuel runs out and their cores “implode into a point of infinite density”. The “rebound” that follows produces a supernova explosion that blows away the outer layers of the star. But the gravity of the collapsed star is so great that, within a boundary called the “event horizon”, nothing is able to escape, not even light. And that’s why we can’t see a black hole, astronomers say.
Astronomers also say that the gravitational tug of a black hole is sufficient to distort Einstein’s “space-time fabric”. And that means it could affect the movement of matter falling into this celestial glutton.
The X-ray emissions from GRO J1655-40 are sporadic—long periods of relative calm followed by shorter periods of more intense activity with emissions millions of times greater than during the quiescent phase.
As reported on Space.com, some scientists began to wonder if the blinking pattern of X-ray activity is “related to how matter accumulates around the black hole”. The black hole is said to be stealing gas from a companion into an “accretion disk” around the super-dense relic, and the scientists suggested that as the mass of the disk accumulates for several years, the black hole consumes very little of the gas, and X-ray emissions are minimal.
“Every few years, however, something—scientists aren’t sure what—triggers a sudden binge fest on the part of the black hole, causing it to guzzle down most of matter in the disk within a period of only a few months”. This is when the profusion of X-rays occurs, the scientists suggested. (See “ Black Hole Puts Dent In Space-time”, January 24, 2006),
But NASA’s Rossi X-ray Timing Explorer recorded something curious. Among the X-ray frequencies observed in 1996 were one at 450 Hz and one at 300 Hz. The same two frequencies were observed again in 2005.
"Because it’s very hard to get gas to behave the same way twice, it argues strongly that these frequencies are being anchored by the black hole’s mass and spin”, study co-author Jon Miller of the University of Michigan told SPACE.com.
The scientists were reminded of the weird things predicted by Einstein’s theory of general relativity. “Because the black hole is so massive and spinning so fast, it warps spacetime around it”. And the more massive the object, the more spacetime is distorted. “If the massive object is also spinning, it causes spacetime to not only bend but to twist as well”.
The authors suggest that the particles moving in “warped spacetime” near the black hole exhibit two types of motions, each producing a unique frequency. “One motion is the orbital motion of the gas as it goes around the black hole. This produces the 450 Hz frequency. The lower 300 Hz frequency is caused by the gas wobbling slightly due to the spacetime deformations”.
"If spacetime were not curved, we’d probably just see one peak," said study co-author Jeroen Homan from the Kavli Institute for Astrophysics and Space Research at MIT.
The authors seemed confident that they were on the right track, and few
astronomers raised objections. "We can now begin to determine the
spin and thus, for the first time, more completely describe the
black hole," Miller said.
Though the photograph above is at best only marginally relevant, we have tried to be as accurate as possible in paraphrasing the logic that two scientists applied to the X-ray emissions from GRO J1655-40. Can you track the number of speculations in their reasoning? Can you separate what is known from what is imagined? If this seems difficult, that is because the language used by scientific media continually confuses fact and theory.
The light source in Scorpius is a fact. So are the sporadic X-ray emissions. But it may surprise you to hear that everything else discussed in the report is speculation, unsupported by anything we can actually study in nature: the star running out of fuel, the implosion, the rebound, the imploded star, its “infinite density”, the “spacetime fabric”, the stellar black hole, the “event horizon”, the companion star, the siphoning of the companion’s gases, the “accretion” disk, the “sudden binge fest”, X-ray production by accumulating matter, the calculated “spin-rate”, the simultaneous “bending and twisting of spacetime”, X-ray frequencies linked to orbital motion of gases, and X-ray frequencies linked to “wobbling” of gases due to “spacetime deformation”.
So it is not unreasonable to pose the question: Does the activity of GRO J1655-40 really imply a “dent in the space-time fabric”? Or is there a much simpler explanation based on accessible natural phenomena?