[wefarrell]

This discovery didn't actually involve LIGO, nor any other feats of impressive physical engineering. It was made by observing neutron stars and finding patterns in their unexpected perturbations.

Neutron star rotation is so consistent that they are used to calibrate atomic clocks[0]. However some of them were glitching and not rotating as expected, but the glitches were consistent between each other. It turns out they aren't actually glitching, but spacetime is being distorted by massive gravitational waves.

[0] https://gizmodo.com/scientists-use-spinning-neutron-stars-to...

[sliken]

Indeed, and part of the magic is knowing jupiters position with a very high precision. Said precision was delivered by the Juno probe in 2016 or so. With that precision we now know the earth position with much more accuracy. The trick is the jupiter and sun orbit around a point outside the surface of the sun. Said point (barycenter) is the point the earth rotates around.

The increased positional accuracy of the earth allows teasing out the distortion from to various pulsars to use the galaxy as a ligo like gravity wave detector.