Get ready for a mind-blowing cosmic revelation! Scientists have potentially uncovered a groundbreaking event, a superkilonova, an extraordinary phenomenon where a star explodes not once, but twice, in dramatically different ways.
Led by Caltech researchers, this discovery is a game-changer, offering a glimpse into the first-ever superkilonova. It all started with a gravitational wave detection earlier this year, which led to a series of observations and a potential breakthrough.
Supernovas, typically caused by the collapse and explosion of rapidly spinning massive stars, often leave behind neutron stars. However, kilonovas, on the other hand, are born from the energetic mergers of two neutron stars, usually starting as a binary system. These mergers create gravitational waves, rippling through spacetime like a cosmic bell.
When the LIGO-Virgo-KAGRA collaboration detected such waves on August 18, 2025, astronomers embarked on a hunt for a cataclysmic collision. Within hours, they found an intriguing object, AT2025ulz, 1.3 billion light-years away, rapidly fading.
This event resembled the only other confirmed kilonova, GW170817, discovered in 2017. Both showed the creation of heavy elements like gold, indicating an energetic collision. But here's where it gets controversial: AT2025ulz's glow faded, then brightened again, revealing hydrogen in its spectra, typical of a supernova.
So, was it a supernova or a kilonova? The researchers suggest it was both. Past studies have hypothesized that supernovas can, on rare occasions, produce two neutron stars, not just one. If these stars collide immediately, they might create a kilonova-like gravitational wave signal.
But this time, the merger occurred within the exploding star, blocking the kilonova signal with the star's massive ejected mass. Additionally, one of the colliding objects was surprisingly small, challenging our understanding of stellar evolution.
Neutron stars are predicted to have a size limit between 2.2 and 3 solar masses, but in theory, they can be as small as 0.1 solar masses. There are two possible ways to create sub-stellar neutron stars from a supernova: fission or fragmentation.
In fragmentation, a rapidly spinning massive star collapses into a large spinning gas disk, which then fragments into smaller clumps, collapsing into low-mass neutron stars within seconds. It's like a cosmic version of planet formation around proto-stars.
This indefinite result reminds us that the universe is full of endless mysteries and fascinating phenomena with multiple interpretations. More research is needed to confirm the superkilonova and similar events. As Mansi Kasliwal, the study's first author, concludes, future kilonovae events might not resemble GW170817 and could be mistaken for supernovae.
The research is published in The Astrophysical Journal Letters, opening up a new chapter in our understanding of the cosmos.
