A recent astronomical discovery has produced the first evidence of a rare cosmic event termed a “superkilonova.” Researchers from the California Institute of Technology detailed their findings in a paper published in The Astrophysical Journal Letters, highlighting a stellar explosion that likely results from the merger of two neutron stars and a supernova.
This event, designated AT2025ulz, stands out as potentially the second kilonova ever detected and the first to originate from such a complex series of interactions. Kilonovas occur when neutron stars collide, resulting in a massive release of energy and heavy elements. In this instance, a supernova appears to have given rise to two neutron stars, which subsequently merged to generate the kilonova.
The broader significance of such cosmic events is profound. Supernovae and kilonovae contribute essential elements, such as carbon, iron, gold, and uranium, to the universe. These elements serve as the building blocks for stars and planets, playing a critical role in the evolution of the cosmos. Furthermore, these explosive phenomena create gravitational waves—ripples in spacetime detected here on Earth by facilities like LIGO.
In August 2023, LIGO alerted the astronomical community to a signal resembling the first kilonova detection from 2017. Following this alert, survey cameras observed rapidly fading red lights, indicating heavy element production characteristic of kilonovas. Shortly after, the source produced a blue flash, suggesting a supernova-like event.
Mansi Kasliwal, the lead author of the study and an astrophysicist at Caltech, described the initial observations: “At first, for about three days, the eruption looked just like the first kilonova in 2017. Everybody was intensely trying to observe and analyze it, but then it started to look more like a supernova, and some astronomers lost interest. Not us.”
For Kasliwal and her team, the characteristics of AT2025ulz raised numerous questions. The event did not align with typical supernova behavior nor with the kilonova observed in 2017. Additionally, LIGO’s gravitational wave data indicated the merger involved two neutron stars, one of which was remarkably light.
Brian Metzger, a theoretical physicist at Columbia University and co-author of the study, noted the significance of the findings: “No neutron star had ever been observed before with a mass less than that of the Sun, and it was believed to be theoretically impossible.” Yet, LIGO detected the explosion from a sub-solar neutron star engaged in a merger.
Researchers propose that the lightweight neutron stars may result from a rapidly spinning massive star that split into two during a supernova explosion. This chaotic process could then lead to the formation of a kilonova as the neutron stars spiral inward.
While the discovery of AT2025ulz suggests a new category of cosmic events, researchers emphasize the need for further investigation. “Future kilonovae events may not look like GW170817 and may be mistaken for supernovae,” Kasliwal stated. “We do not know with certainty that we found a superkilonova, but the event nevertheless is eye-opening.”
As the scientific community continues to analyze these findings, the implications for our understanding of stellar evolution and element formation in the universe are becoming clearer. The study of such extraordinary phenomena not only enhances our knowledge of the cosmos but also inspires curiosity about the origins of the elements that make up the world around us.
