Illustration of two black holes merging, of comparable mass to what LIGO saw. Image credit: XS, the Simulating eXtreme Spacetimes (SXS) project (http://www.black-holes.org).

Dark Matter Winners And Losers In The Aftermath Of LIGO

We’ve come so far since 2015; what do we know about dark matter now that we didn’t know then?

Back in 2015, the dark matter situation was pretty straightforward: the large-scale structure in the Universe demanded that there be a large amount of cold dark matter, and alternatives were struggling to reproduce those successes. Einstein’s General Relativity still needed to work on all scales, from local, Solar System-based tests up to cosmic ones, but there were no direct tests of some of its greatest, strong-field predictions. All of that changed two years ago, with the first announced detection of gravitational waves, courtesy of two merging black holes.

During both Run I and Run II, LIGO, later joined by the Virgo detector, has detected five black hole-black hole merging pairs, along with one merging neutron star pair. Image credit: LIGO scientific collaboration.

Now, as we approach the end of 2017, we’ve used gravitational wave astronomy to detect five merging black holes and a pair of merging neutron stars, a remarkable result all on its own. Yet these detections provide us with a wealth of data about dark matter and its alternatives, replete with winners and losers. In the context of the full suite of evidence, here’s what we know.