PULLMAN, Wash. — Washington State University was approved for membership in the Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration last week. A team of WSU astronomers will contribute to the project, which, beginning this summer, will try to detect gravitational waves that originate from outer space.
Gravitation waves are ripples in the curve of space-time caused by cosmic events. Gravitational waves pass through matter, including the earth, and can be measured as they alternately stretch and shrink distances, which they do on an extremely small scale.
Gravitational waves were predicted by Einstein’s Theory of Relativity and have been inferred from observed changes in the orbit of a binary pulsar system of neutron stars, but have never been confirmed by being measured as they affect earth.
LIGO is a two-part facility designed to detect cosmic gravitational waves by measuring ground movements. LIGO’s instruments are designed to register movements in the earth less than one-trillionth the diameter of a hair. Each laser interferometer facility is an L-shaped system of vacuum tubes, two and one half miles on a side, with mirrors suspended at each end and at the junction. Within the tubes, precision laser beams will sense motion in the mirrors caused by gravitational waves.
The widely separated units, one at Hanford, Wash., and the other near Baton Rouge, La., operate in unison. Since wave-caused movement is similar to that caused by noise, moving equipment or earthquakes, having two facilities at a distance from each other permits researchers to eliminate erroneous readings. Because of the distance, researchers also will be able to use the time lag between the arrival of a wave at one installation and its arrival at the second, to triangulate the direction of the wave’s source in the universe. Locating wave sources also will be enhanced by using information from interferometers in Germany, Italy and Japan.
Gravitational waves are expected to reveal a great deal about the universe including its history, including the Big Bang and its ultimate fate. They also may carry information about black holes, supernovae and neutron stars, and assist researchers in estimating cosmological distances.
WSU’s two new astronomy faculty members have research interests that will benefit from membership in LIGO. Sukanta Bose, who presented WSU’s membership proposal to the LIGO Council in Louisiana last week, works on locating astrophysical and cosmological sources for gravitational waves and is formulating strategies for detecting them. Guy Worthey will use LIGO data for his research on the evolution and the population of stars. The third WSU team member is Shawn Seader, a physics graduate student.
LIGO is being built by the California Institute of Technology and the Massachusetts Institute of Technology with funding from the National Science Foundation. WSU is the only LIGO member in Washington state.