It is widely known that supernova explosions are pre-requisite for creating all elements heavier than hydrogen & helium in the cosmos. Elements like carbon, oxygen, potassium, calcium, iron, silicon, magnesium etc. are all forged in massive stars during its evolution and are ejected into the cosmos during the explosion. During the actual explosion, when the temperatures soar to more than a billion degrees kelvin, the heaviest of elements like gold, silver, platinum, all the way up to Uranium are forged in trace quantities.
However now it has been established that appreciable quantities of these heaviest elements can be forged only during the merger of neutron stars. Kilinovas could be more commonplace than once thought in our galaxy since neutron star pairs could be abundant without us knowing about them.
Just checked on the definition – Yes – A kilonova (also called a macronova or r-process supernova) is a transient astronomical event that occurs in a compact binary system when two neutron stars or a neutron star and a black hole merge into each other.
I think the idea that only standard supernovae are where these elements are forged is rapidly going out of date helped by the incredible findings from the new science of gravitational-wave astronomy. It will be especially interesting to learn more about the very early universe and whether scope existed for creating heavy elements by collisions when space-time was much more condensed.