stomy
30th September 2011, 20:57
In physics, gravitational waves are theoretical ripples in the curvature of spacetime which propagates as a wave, traveling outward from the source. Predicted to exist by Albert Einstein in 1916 on the basis of his theory of general relativity,[1] gravitational waves theoretically transport energy as gravitational radiation. Sources of gravitational waves could possibly include binary star systems composed of white dwarfs, neutron stars, or black holes. The existence of gravitational waves is possibly a consequence of the Lorentz invariance of general relativity since it brings the concept of a limiting speed of propagation of the physical interactions with it. Gravitational waves cannot exist in the Newtonian theory of gravitation, since in it physical interactions propagate at infinite speed.
Although gravitational radiation has not been directly detected, there is indirect evidence for its existence. For example, the 1993 Nobel Prize in Physics was awarded for measurements of the Hulse-Taylor binary system which suggests gravitational waves are more than mathematical anomalies. Various gravitational wave detectors exist. However, they remain unsuccessful in detecting such phenomena.
Source: wikipedia.org
Introduction to LIGO & Gravitational Waves
Sources of Gravitational Waves
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3D visualization of gravitational waves produced by 2 orbiting black holes. [Image: Henze, NASA]
3D Visualization of Gravitational Waves Produced by 2 Black Holes
In general, any acceleration that is not spherically or cylindrically symmetric will produce a gravitational wave. Consider a star that goes supernova. This explosion will produce gravitational waves if the mass is not ejected in a spherically symmetric way, although the center of mass may be in the same position before and after the explosion. Another example is a spinning star. A perfectly spherical star will not produce a gravitational wave, but a lumpy star will.
The gravitational waves that modern detectors are sensitive to would be in the audible frequency range if they were sound waves. In that sense, these detectors can be thought of as ‘gravitational wave radios.’ Just like radio waves cannot be heard without a radio to detect the radio waves and decode the music signal to send to the speakers, gravitational waves cannot be heard without a detector to distinguish the gravitational wave and send that signal to speakers. All of the physics that went into the production of a gravitational wave is then encoded in this ‘music’ for physicists to decode. In the following descriptions of gravitational waves, the ‘sound’ they make will often be described to illustrate the properties of the expected signal.
Listen to an example signal of two neutron stars merging.
Listen to the same signal mixed in with noise. Noise in the LIGO detectors are mostly caused by vibrations from the local environment.
There are four main sources of gravitational waves caused by different kinds of motion and changing distributions of mass - continuous, inspiral, burst, and stochastic.
Source: ligo.org
The most interesting is the gravitational wave "Inspiral":
Inspiral Gravitational Waves
10166
An artist's impression of two stars orbiting each other and progressing (from left to right) to merger with resulting gravitational waves. [Image: NASA]
Binary Inspiral Pregression
Inspiral gravitational waves are generated during the end-of-life stage of binary systems where the two objects merge into one. These systems are usually two neutron stars, two black holes, or a neutron star and a black hole whose orbits have degraded to the point that the two masses are about to coalesce. As the two masses rotate around each other, their orbital distances decrease and their speeds increase, much like a spinning figure skater who draws his or her arms in close to their body. This causes the frequency of the gravitational waves to increase until the moment of coalescence. The sound these gravitational waves would produce is a chirp sound (much like when increasing the pitch rapidly on a slide whistle) since the binary system’s orbital frequency is increasing (any increase in frequency corresponds to an increase in pitch). (Listen)
10167
An example signal from an inspiral gravitational wave source. [Image: A. Stuver/LIGO]
Example Inspiral Waveform
Source: ligo.org
Different study sites around the world:
10165
Interferometric Experiments
ACIGA: AustralianConsortium for Interferometric Gravitational wave Astronomy
GEO600: a British/German Collaboration
LIGO: C.I.T. - M.I.T.Collaboration
LISA: Laser interferometryin the space
TAMA: The Experimentin Japan
Resonant Bar Experiments
The ROG Group
The AURIGA Experiment
The GRAILExperiment
Other GW Related Web Sites
The GREX committee
EAS/EPS Gravity Physics Section
Source: cascina.virgo.infn.it
Source: http://revivall.over-blog.com/article-etude-des-sources-d-ondes-gravitationnelles-study-of-sources-of-gravitational-waves-85526130.html
Others articles available on link:
The planet with two suns of Luke Skywalker discovered in our galaxy
The planets traveling solo
hopi prophecy: elenin and planet x
Although gravitational radiation has not been directly detected, there is indirect evidence for its existence. For example, the 1993 Nobel Prize in Physics was awarded for measurements of the Hulse-Taylor binary system which suggests gravitational waves are more than mathematical anomalies. Various gravitational wave detectors exist. However, they remain unsuccessful in detecting such phenomena.
Source: wikipedia.org
Introduction to LIGO & Gravitational Waves
Sources of Gravitational Waves
10168
3D visualization of gravitational waves produced by 2 orbiting black holes. [Image: Henze, NASA]
3D Visualization of Gravitational Waves Produced by 2 Black Holes
In general, any acceleration that is not spherically or cylindrically symmetric will produce a gravitational wave. Consider a star that goes supernova. This explosion will produce gravitational waves if the mass is not ejected in a spherically symmetric way, although the center of mass may be in the same position before and after the explosion. Another example is a spinning star. A perfectly spherical star will not produce a gravitational wave, but a lumpy star will.
The gravitational waves that modern detectors are sensitive to would be in the audible frequency range if they were sound waves. In that sense, these detectors can be thought of as ‘gravitational wave radios.’ Just like radio waves cannot be heard without a radio to detect the radio waves and decode the music signal to send to the speakers, gravitational waves cannot be heard without a detector to distinguish the gravitational wave and send that signal to speakers. All of the physics that went into the production of a gravitational wave is then encoded in this ‘music’ for physicists to decode. In the following descriptions of gravitational waves, the ‘sound’ they make will often be described to illustrate the properties of the expected signal.
Listen to an example signal of two neutron stars merging.
Listen to the same signal mixed in with noise. Noise in the LIGO detectors are mostly caused by vibrations from the local environment.
There are four main sources of gravitational waves caused by different kinds of motion and changing distributions of mass - continuous, inspiral, burst, and stochastic.
Source: ligo.org
The most interesting is the gravitational wave "Inspiral":
Inspiral Gravitational Waves
10166
An artist's impression of two stars orbiting each other and progressing (from left to right) to merger with resulting gravitational waves. [Image: NASA]
Binary Inspiral Pregression
Inspiral gravitational waves are generated during the end-of-life stage of binary systems where the two objects merge into one. These systems are usually two neutron stars, two black holes, or a neutron star and a black hole whose orbits have degraded to the point that the two masses are about to coalesce. As the two masses rotate around each other, their orbital distances decrease and their speeds increase, much like a spinning figure skater who draws his or her arms in close to their body. This causes the frequency of the gravitational waves to increase until the moment of coalescence. The sound these gravitational waves would produce is a chirp sound (much like when increasing the pitch rapidly on a slide whistle) since the binary system’s orbital frequency is increasing (any increase in frequency corresponds to an increase in pitch). (Listen)
10167
An example signal from an inspiral gravitational wave source. [Image: A. Stuver/LIGO]
Example Inspiral Waveform
Source: ligo.org
Different study sites around the world:
10165
Interferometric Experiments
ACIGA: AustralianConsortium for Interferometric Gravitational wave Astronomy
GEO600: a British/German Collaboration
LIGO: C.I.T. - M.I.T.Collaboration
LISA: Laser interferometryin the space
TAMA: The Experimentin Japan
Resonant Bar Experiments
The ROG Group
The AURIGA Experiment
The GRAILExperiment
Other GW Related Web Sites
The GREX committee
EAS/EPS Gravity Physics Section
Source: cascina.virgo.infn.it
Source: http://revivall.over-blog.com/article-etude-des-sources-d-ondes-gravitationnelles-study-of-sources-of-gravitational-waves-85526130.html
Others articles available on link:
The planet with two suns of Luke Skywalker discovered in our galaxy
The planets traveling solo
hopi prophecy: elenin and planet x