August the 17th 2017, the VIRGO and LIGO interferometers observed gravitational waves
generated by a NSM, one thousand of billions of billions of kilometers far from us (the light produced
by that merging travelled for 130 million years to arrive here... this means that the event
occurred when the dinosaurs were still alive on the Earth, in the Cretaceous period).
In the days after the detection of gravitational waves from GW180817
(this is the name assigned to the source), basically all telescopes on the world pointed toward it.
The reason is simple: observe
an increase of the lightcurve after 4-5 days from the stellar merging
(see e.g. the web pages of the Italian INAF
GRAWITA collaboration).
Such an increase of the luminosity (indeed observed) is the smoking gun that, during the NSM,
an enormous amount of heavy elements were formed through the r process.
The presence of those metals (in particular the lanthanides), in fact,
ensures that the structure is warmed up by their decay (during this process a lot of light is produced,
which interacts with the stellar gas, heating it).
Actually, the r process nucleosynthesis is more complex, because the high neutron flux leads to the
production of Actinides. Those isotopes have very small lifetimes, because
they fissionate spontaneously (or as a result of a neutron capture), that is they break in two lighter
nuclei, producing new neutrons. The "pieces" of a recently fissionated actinide, however, may in turn capture neutrons.
A cyclical process then sets up, named “fission recycling”. Such a process
determines the fact that r process nucleosynthesis (in particular the heaviest isotopes)
is almost independent on the physical conditions of the merger.
NSMs produce a plethora of chemical elements (see Figure 11). Some of these elements are known
(and are very precious, as gold or silver),
while others are completely unknown and have almost unpronounceable names.
Without them, however, modern technology would not have developed: for instance, we could mention
europium
(essential to create colors in modern televisions) or
erbium (without which we would not have fast optic fibers).
And what about modern cellphones...???