For the first time, astronomers have positively identified a binary system that is destined to one day end up as a kilonova – the explosive result of a neutron star collision.

"These new results demonstrate that, in at least some cases, two sibling neutron stars can merge when one of them was created without a classical supernova explosion."

Neutron star collisions are rare, but they play an important role in seeding the Universe with heavy elements such as gold, platinum, and uranium.

Instead, these elements are formed in energetic events, such as kilonovae: we have evidence of this from GW170817, the history-making neutron star collision observed by telescopes around the world.

"The star was so depleted that the explosion didn't even have enough energy to kick the orbit into the more typical elliptical shape seen in similar binaries," Richardson says.

"As we understand the growing population of systems like CPD-29 2176 we will gain insight into how calm some stellar deaths may be and if these stars can die without traditional supernovae."