Astronomers have spotted Strontium in the aftermath of a collision between two neutron stars. This is the first time a heavy element has ever been identified in a kilonova, the explosive aftermath of these types of collisions. The discovery plugs a hole in our understanding of how heavy elements form.
In 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the European VIRGO Observatory detected gravitational waves coming from the merger of two neutron stars. The merger event was named GW170817, and it was about 130 million light-years away in the galaxy NGC 4993.
The resulting kilonova is called AT2017gfo, and the European Southern Observatory (ESO) pointed several of their telescopes at it to observe it in different wavelengths. In particular, they pointed the Very Large Telescope (VLT) and its X-shooter instrument at the kilonova.