Supernovae are the spectacular explosions that result from dying massive stars, littering the universe with heavy elements like carbon and iron. Kilonovae form when two binary neutron stars begin to orbit in their death spiral, emitting powerful gravitational waves and stripping apart neutron-rich matter. Then the stars collide and merge, creating a hot cloud of debris that glows with multi-wavelength light. It is the neutron-rich debris that astronomers believe creates the visible and infrared light of a kilonova. The glow is brighter in the infrared than in the visible spectrum, a characteristic signature that results from heavy elements in the ejecta that block the visible light but allow the infrared to pass through.
This latest kilonova candidate event, named AT2025ulz, initially resembled the 2017 event, but over time its properties began to resemble a supernova, making it less interesting to many astronomers. But it wasn't a classic supernova either. Therefore, some astronomers continued to monitor the event and analyze combined 'multisensor' data from other collaborations and telescopes during the same time frame. They concluded that this was a multi-stage event: a supernova produced twin baby neutron stars, which then merged to form a kilonova. That said, the evidence is not strong enough to claim that this definitely happened; astronomers need to find more such superkilnovae to confirm this.
DOI: Astrophysical Journal Letters, 2025. 10.3847/2041-8213/ae2000 (About DOIs).
The fingerprint of an ancient seafarer
Credit: Photography by Erik Johansson, 3D model by Sahel Ganji
In the 4th century BC, an invading mini-armada of about four boats attacked an island off the coast of Denmark. The attack failed and the victorious islanders celebrated by sinking one of the boats, filled with their enemies' weapons, into a swamp, where it remained until discovered by archaeologists in the 1880s. It is known as the Hjortspring boat, and archaeologists were recently surprised when their analysis revealed an intact human fingerprint in the tar used to waterproof the ship. They described their discovery in an article published in the journal PLoS ONE.
