by Clifford M. Will, CQG Editor-in-Chief
What a week for gravitational physics!
First came the September 27th announcement of another detection of gravitational waves, this time by the three-detector network that included Virgo along with the two LIGO observatories. The source of the gravitational waves was another fairly massive black hole binary merger, with black holes of 30 and 26 solar masses. Once again, about 3 solar masses were converted to energy in a fraction of a second, leaving behind a 53 solar mass black hole spinning at about 70 percent of the maximum allowed. With Virgo included in the detection, the localization of the source on the sky was improved dramatically over earlier detections by LIGO alone, dropping to a small blob on the sky measuring 60 square degrees, from the large, 1000 square degree banana-shaped regions of earlier detections.
For the first time, a test of gravitational-wave polarizations was carried out. Because the arms of the two LIGO instruments are roughly parallel, they have very weak sensitivity to different polarization modes of the waves. But with Virgo’s very different orientation, it was possible to show that the data favor the two spin-2 modes of general relativity over pure spin-0 or pure spin-1 modes.
But then, six days later came the announcement of the Nobel Prize in Physics, awarding one half of the prize to Rainer Weiss of MIT and the other half shared between Kip Thorne and Barry Barish of Caltech, for decisive contributions to the detection of gravitational radiation. CQG congratulates the winners!