Religions > Atheism > Black hole puts dent in space-time Scientists deduce its existence from X-ray frequencies
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Religions > Atheism |
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"stoney" |
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25 Jan 2006 05:25:03 PM |
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Black hole puts dent in space-time Scientists deduce its existence from X-ray frequencies |
http://www.msnbc.msn.com/id/11009343/
Black hole puts dent in space-time
Scientists deduce its existence from X-ray frequencies
By Ker Than
Space.com
Updated: 7:33 p.m. ET Jan. 24, 2006
A spinning black hole in the constellation Scorpius has created a stable
dent in the fabric of space-time, scientists say.
The dent is the sort of thing predicted by Albert Einstein’s theory of
general relativity. It affects the movement of matter falling into the
black hole.
The space-time dent is invisible, but scientists deduced its existence
after detecting two X-ray frequencies from the black hole that were
identical to emissions noted nine years ago. The finding will allow
scientists to calculate the black hole’s spin, a crucial measurement
necessary for describing the object’s behavior.
Black holes form when very massive stars runs out of fuel. Their cores
implode into a point of infinite density and their outer layers are
blown away in a powerful supernova explosion. Within a theoretical
boundary called the event horizon, the black hole’s gravity is so strong
that nothing, including light, can escape.
The X-ray frequencies detected by the team of researchers came from
outside the event horizon of GRO J1655-40, a black hole located roughly
10,000 light-years from Earth. It is about seven times more massive than
the Sun and siphoning gas from a nearby companion star.
GRO J1655-40 undergoes short periods of intense X-ray emissions,
followed by longer periods of comparative quiet. Scientists think this
blinking pattern of X-ray activity is related to how matter accumulates
around the black hole.
Gas siphoned from the companion star builds up steadily in an accretion
disk around the black hole. This process continues for several years.
While the accumulation is taking place, the black hole consumes very
little gas from the disk.
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.
Black holes emit millions of times more X-rays during these periods of
increased activity than when they’re quiet.
In recent years, NASA’s Rossi X-ray Timing Explorer has caught GRO
J1655-40 binging twice, once in 1996 and again in 2005. Among the X-ray
frequencies observed in 1996 was one at 450 Hz and one at 300 Hz. These
two frequencies were observed again in 2005.
This was surprising because when it comes to X-ray emissions, black
holes are not known for stability. X-rays are emitted from particles of
superheated gas as they swirl into a black hole and rub against each
other. However, the luminosity and the frequency at which the X-rays
flicker varies from moment to moment because the rate at which the black
hole consumes the gas is not constant.
Therefore, detecting two stable frequencies nine years apart strongly
suggests they are not caused by fluctuations in the black hole’s gas
consumption, but by something else.
"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, fundamental properties of the black hole itself,"
study co-author Jon Miller of the University of Michigan told SPACE.com.
Because the black hole is so massive and spinning so fast, it warps
space-time around it.
Space-time
While devising his general theory of relativity, Einstein combined the
three dimensions of space and the one dimension of time into a single
useful concept he called space-time.
space-time can be thought of as an elastic sheet that bends under the
weight of objects placed upon it. The more massive the object, the more
space-time bends. If the massive object is also spinning, it causes
space-time to not only bend but to twist as well. Scientists call this
effect "frame dragging."
Twisted space-time will cause gas falling into a black hole to move in
certain ways. The phenomenon can be roughly compared to the movement of
a needle on a record player: as the needle moves along an etched groove
on a record, it produces a sound, the exact nature of which is
determined by physical deformations in the groove itself.
Similarly, the black hole has created stable deformations in the fabric
of space-time that affects matter moving around it. Gas swirling around
the black hole acts like the record needle, but instead of producing
specific sounds, it produces certain frequencies of X-ray light.
Two peaks
Scientists think that gas particles moving in warped space-time near the
black hole exhibit two types of motions, each giving rise to 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 space-time
deformations.
"If space-time 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.
Scientists think that all spinning black holes emit two stable
frequencies, and that the frequencies are closely tied to the black
hole’s mass and spin.
GRO J1655-40’s mass had already been calculated based on observations of
the companion star’s orbit. The missing piece of information was the
black hole’s spin rate. The new frequency findings will help resolve
this problem.
"We can now begin to determine the spin and thus, for the first time,
more completely describe the black hole," Miller said.
The finding was announced earlier this month at a meeting of the
American Astronomical Society.
© 2006 Space.com
--
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| User: "johac" |
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| Title: Re: Black hole puts dent in space-time Scientists deduce its existence from X-ray frequencies |
26 Jan 2006 01:16:55 AM |
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In article <552gt1p7pvoeri1vlvqucc221tm14otn8p@4ax.com>,
stoney <stoney@the.net> wrote:
http://www.msnbc.msn.com/id/11009343/
Black hole puts dent in space-time
Scientists deduce its existence from X-ray frequencies
By Ker Than
Space.com
Updated: 7:33 p.m. ET Jan. 24, 2006
A spinning black hole in the constellation Scorpius has created a stable
dent in the fabric of space-time, scientists say.
The dent is the sort of thing predicted by Albert Einstein’s theory of
general relativity. It affects the movement of matter falling into the
black hole.
The space-time dent is invisible, but scientists deduced its existence
after detecting two X-ray frequencies from the black hole that were
identical to emissions noted nine years ago. The finding will allow
scientists to calculate the black hole’s spin, a crucial measurement
necessary for describing the object’s behavior.
Interesting.
--
John Hachmann aa #1782
"Those who can make you believe absurdities can make you commit atrocities"
-Voltaire
Contact - Throw a .net over the .com
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