Distorted
Rotating
Colliding

Chapter 3.4 What Will LIGO Observe?

Gravitational waves triggered by cosmic events should cause specific displacements resulting in unique interference patterns. Converting these patterns into the more familiar squiggles of an oscilloscope, or "waveforms," will yield significant information about the source. However, because the first signals to be detected will likely be so weak, it may be difficult to discern true signals from "noise." In some cases, where the source of the gravitational wave is known through corroborating evidence -- electromagnetic radiation emitted by a supernova, for example -- researchers will be able to more easily confirm and pinpoint the event causing the gravitational disturbance.
However, assigning observed waveforms to specific events will require overlaying them on templates that are now being created via supercomputer simulations of these same events.

One of the Grand Challenge goals of the research described in this exhibit is to build a catalog of predicted waveforms. Then, when scientists succeed in building detectors sensitive enough to detect the subtle oscillations that reveal a passing gravitational wave, they'll be able to deduce the type of event that triggered it, and the properties of the object it came from.

Here are four waveforms computed on supercomputers at NCSA.

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Spiralling to Final Merger

Hunting for Gravitational Waves

There are no lack of candidates in Einstein's Relativistic Universe. Powerful gravitational waves are thought to be generated by non-spherical, large-scale vibrations of spacetime -- such as occur when a star explodes and its core collapses, two neutron stars collide, or two black holes spiral towards each other, then coalesce.
But will LIGO perform as required? According to its designers, the instrument's extreme sensitivity should suffice to pick out even the tiniest displacements from "noise." Over a fairly broad frequency range, LIGO's projected sensitivity should match the calculated gravitational wave amplitudes for a variety of sources.

LIGO's Projected Sensitivity

In this diagram, the amplitude of the displacement measured by LIGO resulting from a passing gravitational wave is plotted against the wave's frequency in cycles per second or Hertz (Hz).
The LIGO scientists are confident they'll be able to detect a variety of cataclysms, each taking place upwards of a hundred million light years away, including colliding neutron stars, coalescing black holes, and a collapsing star.
If you would like to find out more about gravitational wave detectors, visit LIGO's home page at Caltech or check out VIRGO's in Pisa, Italy. But please come back! There's a lot more ahead -- movies too!