A chirp, then a new light in NGC 4993

On 17 August 2017 a chirp lasts about a hundred seconds in the LIGO detectors, with Virgo helping to place it. Two neutron stars have spiraled in. Within hours a new point of light is found in the galaxy NGC 4993. The community, not a single hero, photographs the fade in every band they have.

This is a dead-star story that becomes a factory story. The glow is a kilonova. The spectrum carries freshly made heavy nuclei. Gold, platinum, the lanthanides: not only in a 1957 paper now, but in a week of telegrams.

Neutron-star mergers are a site of r-process nucleosynthesis. B²FH had the outline. 2017 has the event. Hubble and ground telescopes watch a thing no one had seen this clearly: two pulsars’ cousins becoming light, and a little of the periodic table.