# Gravitational Wave Theory

Einstein's theory of General Relativity predicts that accelerating massive bodies will produce gravitational waves, vibrations in the fabric of spacetime.

On 11 February 2016, the LIGO and Virgo Scientific Collaboration announced they had made the first observation of gravitational waves, confirming Einstein’s prediction. The observation itself was made on 14 September 2015, using the Advanced LIGO detectors. The gravitational waves originated from a pair of merging black holes. After the initial announcement the LIGO instruments detected two more confirmed, and one potential, gravitational wave events. In August 2017, the two LIGO instruments, and the Virgo instrument, observed a fourth gravitational wave from merging black holes, and a fifth gravitational wave from a binary neutron star merger.

Several other gravitational-wave detectors are planned or under construction. Space-borne detectors, such as the Laser Interferometer Space Antenna (LISA) mission, are also being planned by both NASA and the European Space Agency. The detection of gravitational waves requires their precise theoretical modeling to allow for the construction of waveform templates with which to filter the noise data.

The eXtreme Gravity Institute at Montana State University (XGI) focuses on the analytical modeling of gravitational waves emitted during the inspiral and merger of compact objects, such as black holes and neutron stars. Such modeling requires the solution to the Einstein equations, which we perform analytically via mathematical series techniques. During the inspiral, when the compact objects have small velocities relative to the speed of light, we employ post-Minkowskian and post-Newtonian techniques to solve the Einstein equations. After the merger, as the remnant compact object settles down to its final stationary state, we employ black hole perturbation theory to solve the field equations. These solutions then allow us to predict the gravitational wave observable from which to construct template filters.

For a general introduction to Gravitational Waves, see our full-dome planetarium show “Einstein’s Gravity Playlist” here: