by Kathy Chambers on Fri, August 12, 2016
Laser Interferometer Gravitational-Wave
Observatory (LIGO) in Livingston, LA.
Image credit: LIGO Laboratory
Interferometers are investigative tools used in many fields in science and engineering. They work by merging two or more sources of light or other waves to create an interference pattern, which can be precisely measured and analyzed. Interferometers are making possible significant advances in scientific research. One of these advances is in astronomy, where laser interferometers are opening a new era in the exploration of the universe.
In 1972, a young Massachusetts Institute of Technology physics professor, Rainer Weiss, drew up a teaching exercise using a basic concept for an interferometer to detect gravitational waves. This work later became the blueprint for the Laser Interferometer Gravitational-Wave Observatory (LIGO), a national facility for gravitational wave research. LIGO is funded by the National Science Foundation and other public and private institutions.
LIGO currently consists of two of the world’s largest and most sensitive interferometers located 1,865 miles apart on DOE’s Hanford Site at Hanford, Washington, and in Livingston, Louisiana, shown in the image above. These incredible laser interferometers operate in unison using laser interferometry to measure the minute ripples in space-time caused by passing gravitational waves from space events. Observed signals from the Hanford and Livingston detectors are then superimposed to verify the gravitational waves and their origin.
LIGO’s search for gravitational waves began in 2002 but no waves were discovered. LIGO was then redesigned making its interferometers 10 times more sensitive, allowing it to probe 1,000 times more volume of space. A deeper search for gravitational waves began in September 2015 with advanced LIGO (aLIGO). On September 14, 2015, the first direct measurement of a gravitational wave was made from merging black holes nearly 1.3 billion light years away. Four months later, aLIGO announced a second gravitational wave detection. These waves were detected 100 years after Albert Einstein’s prediction of gravitational waves in his general theory of relativity. We are now in unchartered territory in space exploration and excitement is mounting across the globe. Additional laser interferometers are coming online in the next few years and the scientific potential to astronomy should be immense.
aLIGO research is carried out by the LIGO Scientific Collaboration, a group made up of more than 1,000 scientists from dozens of institutions and 15 countries worldwide. DOE researchers are participating in this research. Scientists at the Fermi National Accelerator Laboratory and the Dark Energy Survey are helping to follow up on aLIGO’s gravitational wave detections. SLAC National Accelerator Laboratory and Stanford University scientists are using X-rays to improve mirror coatings that determine the experiment’s sensitivity. Over 700 research reports on DOE’s LIGO-related interferometer research endeavors are available in DOE’s SciTech Connect database.
OSTI’s Dr. William Watson discusses the Department’s interferometer and wave research in his latest white paper “In the OSTI Collections: Interferometry.” OSTI’s Science Showcase also spotlights DOE’s interferometer research endeavors.