Gravitational Astronomy Proves its Maturity
With the sighting of a merger between a black hole and a neutron star
On August 14th, just after 9pm Universal Time, a ripple of gravitational waves reached Earth. Until a few years ago no one would have noticed such an event. But 2015 saw the reopening, after an upgrade, of the Laser Interferometer Gravitational-wave Observatory (LIGO), a pair of detectors in Washington state and Louisiana. These were joined in 2017 by Virgo, an upgraded instrument in Italy. Together, the three instruments not only recorded the wave’s passage, they also worked out where in the sky it had come from and then texted that information to the world’s astronomers.
This stimulated the deployment of a host of other devices, to look at the wave’s point of origin near the border between the constellations of Cetus and Sculptor. Telescopes capable of examining all parts of the spectrum, from gamma rays to radio waves, were brought into play. And, courtesy of IceCube, an instrument at the South Pole, the sky was also scanned for tiny particles known as neutrinos that might have been released by whatever humungous event it was that had disturbed the fabric of the space-time continuum to create such a gravitational ripple.
The provisional conclusion of all this “multimessenger” activity is that the…
