Physics Colloquium: "Shining New Light on the Physics of Neutron Star Mergers”

In August 2017, the LIGO/Virgo observatory detected gravitational waves for the first time from the merger of two neutron stars.  This cataclysmic event was followed (within seconds) by a burst of gamma-rays and (within 11 hours) by a bright but rapidly-fading visual-wavelength glow.  The properties of the visual emission matched remarkably well existing predictions for radiation powered by the radioactive decay of heavy nuclei, which were synthesized in the expanding neutron-rich merger debris via the rapid neutron capture process.  I will describe ongoing efforts to interpret LIGO's first merger from both the electromagnetic and gravitational wave sides, and the resulting implications for the origin of the heaviest elements in the universe and the equation of state of nuclear density matter.  I will place these results in the context of discoveries made during LIGO/Virgo's recently concluded O3 run and preview the impending "era of multi-messenger astronomy", when by the end of this decade a new merger is detected every few days.