Scientists from the University of Florida are once again playing a leading role in the search for gravitational waves in the universe

Above: The Laser Interferometer Gravitational-wave Observatories searches for gravitational waves in the universe.

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The Search for Gravity Waves

GAINESVILLE, FL. - Scientists from the University of Florida are once again playing a leading role in the search for gravitational waves in the universe. The Advanced LIGO Project, an upgrade in sensitivity for LIGO (Laser Interferometer Gravitational-wave Observatories), was approved by the National Science Board in its meeting on March 27. The National Science Foundation will fund the $205.12M, seven-year project, starting with $32.75M in 2008. This major upgrade will increase the sensitivity of the LIGO instruments by a factor of 10, giving a one thousand-fold increase in the number of astrophysical candidates for gravitational wave signals. The project is managed by Caltech and MIT, with the UF team playing a leading role developing a key Advanced LIGO subsystem.

According to David Reitze, a professor in the University of Florida Physics Department and head of the LIGO Scientific Collaboration, "gravitational waves are ripples in the space-time fabric that travel to Earth, bringing with them information about their violent origins and about the nature of gravity that cannot be obtained by other astronomical tools." Almost 600 scientists from the US and around the world are active in the LSC in the search for gravitational waves from exotic sources such as co-orbiting black holes and violent supernova explosions.

"We anticipate that this new instrument will see gravitational wave sources possibly on a daily basis, with excellent signal strengths, allowing details of the waveforms to be observed and compared with theories of neutron stars, black holes, and other astrophysical objects moving near the speed of light," adds Jay Marx of the California Institute of Technology, executive director of the LIGO Laboratory.

Gravitational waves are produced by violent events in the distant universe--for example, by the collision of two black holes or by the cores of supernova explosions. Gravitational waves are emitted by accelerating masses much in the same way as radio waves are produced by accelerating charges-- such as electrons in antennas.

The University of Florida designed and built the Input Optics for the original LIGO interferometers located in Livingston, LA and Hanford, WA and will do the same again for Advanced LIGO. The Input Optics is one of seven major subsystems of LIGO, providing critical stabilization of the laser beam used to detect gravitational waves in the ultrahigh precision interferometers. In addition to Reitze, University of Florida professors Guido Mueller and David Tanner will lead the development and construction effort for UF.

Physicists from UF also play a leading role in analyzing the data from the LIGO detectors, searching for gravitational wave 'bursts' from astrophysical sources. "Gravitational wave bursts, once detected, will be a major discovery in astrophysics. Bursts of gravitational waves may be produced by a number of astrophysical events, for example by merging Black holes. It is anticipated that Advanced LIGO will be able to discover such events if their frequency is as predicted by the theory" said Professor Guenakh Mitselmakher, Director of the UF Institute for High Energy Physics and Astrophysics. Mitselmakher, along with Scientist Sergei Klimenko and Professor Bernard Whiting are actively working on analyzing the LIGO data.

Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity, but only since the 1990s has technology become powerful enough to permit detecting them and harnessing them for science.

Although they have not yet been detected directly, the influence of gravitational waves on a binary pulsar system (two neutron stars orbiting each other) has been measured accurately and is in excellent agreement with the predictions. Scientists therefore have great confidence that gravitational waves exist. But a direct detection will confirm Einstein's vision of the waves, and allow a fascinating and unique view of cataclysms in the cosmos.

The Advanced LIGO detector, to be installed at the LIGO Observatories in Hanford, Washington, and Livingston, Louisiana, using the existing infrastructure, will replace the present detector, and will transform gravitational wave science into a real observational tool. David Shoemaker of MIT, the project leader for Advanced LIGO, says the "the improvement of sensitivity will allow the data set generated after one year of initial operations to be equaled in just several hours." The Advanced LIGO upgrade calls for changes in the lasers, optics, seismic isolation systems, and in how the microscopic motion (in the range of 10-20 meters of the test masses is detected.

The change of more than a factor of 10 in sensitivity comes also with a significant increase in the sensitive frequency range, and the ability to tune the instrument for specific astrophysical sources. This will allow Advanced LIGO to look at the last minutes of life of pairs of massive black holes as they spiral closer, coalesce into one larger black hole, and then vibrate much like two soap bubbles becoming one.

It will also allow the instrument to pinpoint periodic signals from the many known pulsars that radiate in the range from 500 to 1000 Hertz (frequencies which correspond to high notes on an organ). Recent results from the Wilkinson Microwave Anisotropy Probe have shown the rich information that comes from looking at the photon, or infrared cosmic background, which originated some 400,000 years after the Big Bang. Advanced LIGO can be optimized for the search for the gravitational cosmic background--allowing tests of theories about the development of the universe only 10-35 seconds after the Big Bang.

The Caltech-MIT LIGO Laboratory will manage the Advanced LIGO project, with contributions from the the United Kingdom Science and Technology Facilities Council and the German Max-Planck Gesellschaft. The instruments will be ready to start scientific operation in 2014.



Guenakh Mitselmakher
Distinguished Professor of Physics
Director, UF Institute of High Energy Physics and Astrophysics (IHEPA)
Principal Investigator, UF LIGO group



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