Why is the discovery of merging neutron stars important?
Reasons why this is important:
- It is the first simultaneous detection of a gravitational wave and electromagnetic signal (and the strongest GW signal yet). It spectacularly corroborates the reality of the GW detection technology and analysis. The progenitor has been unambiguously located in a (relatively) nearby galaxy, allowing a host of other telescopes to obtain detailed measurements.
- It shows that GWs travel at the speed of light, a further verification of Einstein’s General Relativity.
- It shows that most of the very heavy elements such as gold, platinum, osmium etc. are plausibly produced by merging neutron stars and constrains the rate of such mergers in the local universe.
- It shows that short gamma ray bursts – some of the most energetic explosions in the universe – can be caused by neutron star mergers.
- It is the closest detected short gamma ray burst (with a known distance). That the progenitor has also been characterised allows a closer investigation of the interesting physics underlying the ejection and jet mechanisms thought to be responsible for the gamma rays.
- It provides observational constraints on how matter behaves at extremely high densities, testing our understanding of fundamental physics to its limits – for example, the details of the gravitational wave signal moments before merger are diagnostic of the interior conditions of neutron stars at densities of ∼1018∼1018 kg/m33.
- It provides an independent way of measuring the expansion of the universe, because the distance to the GW source pops out of the analysis and can be compared with the redshift of the identified host galaxy. The result agrees with measurements made using the cosmic microwave background and the distance-redshift relation calibrated by other means, verifying our estimation of distances, at least in the local universe.