Free Astronomy Magazine July-August 2023

48 JULY-AUGUST 2023 ASTRO PUBLISHING characteristics and types of stars that make up this system — a neutron star created by an ultra-stripped su- pernova and a closely orbiting mas- sive star that is in the process of becoming an ultra-stripped super- nova itself. An ultra-stripped super- nova is the end-of-life explosion of a massive star that has had much of its outer atmosphere stripped away by a companion star. This class of super- nova lacks the explosive force of a traditional supernova, which would otherwise “kick” a nearby compan- ion star out of the system. “The current neutron star would have to form without ejecting its companion from the system. An ultra-stripped supernova is the best explanation for why these compan- ion stars are in such a tight orbit,” said Noel D. Richardson at Embry- Riddle Aeronautical University and lead author of the paper. “To one day create a kilonova, the other star First kilonova progenitor system identified by NOIRLab − Charles Blue A stronomers using the SMARTS 1.5-meter Telescope at Cerro Tololo Inter-American Obser- vatory in Chile, a Program of NSF’s NOIRLab, have uncovered the first example of a phenomenally rare type of binary star system, one that has all the right conditions to even- tually trigger a kilonova — the ultra- powerful, gold-producing explosion created by colliding neutron stars. Such an arrangement is so vanish- ingly rare that only about 10 such systems are thought to exist in the entire Milky Way Galaxy. The findings are published in the journal Nature . This unusual system, known as CPD-29 2176, is located about 11,400 light-years from Earth. It was first identified by NASA’s Neil Gehrels Swift Observatory. Later observations with the SMARTS telescope allowed astronomers to deduce the orbital T his is an artist’s impression of the first confirmed detection of a star system that will one day form a kilonova — the ultra-powerful, gold-producing explosion created by merging neutron stars. These systems are so phenomenally rare that only about 10 such systems are thought to exist in the entire Milky Way. [CTIO/NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamani]