Introduction to LIGO & Gravitational Waves
Sources of Gravitational Waves
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.
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