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Introduction to LIGO & Gravitational Waves

Inspiral Gravitational Waves

An artist's impression of two stars orbiting each other and progressing (from left to right) to merger with resulting gravitational waves. [Image: NASA/CXC/GSFC/T.Strohmayer]

Binary Inspiral Pregression
Inspiral gravitational waves are generated during the end-of-life stage of binary systems where the two objects merge into one.  These systems are usually two neutron stars, two black holes, or a neutron star and a black hole whose orbits have degraded to the point that the two masses are about to coalesce.  As the two masses rotate around each other, their orbital distances decrease and their speeds increase, much like a spinning figure skater who draws his or her arms in close to their body.  This causes the frequency of the gravitational waves to increase until the moment of coalescence.  The sound these gravitational waves would produce is a chirp sound (much like when increasing the pitch rapidly on a slide whistle) since the binary system’s orbital frequency is increasing (any increase in frequency corresponds to an increase in pitch). (Listen)

An example signal from an inspiral gravitational wave source. [Image: A. Stuver/LIGO]
Example Inspiral Waveform

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