A star just blew up inside a massive, 70,000-light-year-wide ring left over from two galaxies smashing into each other.
arXiv · March 18, 2026 · 2603.15899
The Takeaway
The explosion occurred in a rare 'collisional ring' far from any galaxy center. It suggests that galactic collisions create massive pressure waves that physically shove stars out of their homes and into the void before they explode.
From the abstract
Galaxy mergers can both trigger star formation and rearrange where stars live, producing long-lived tidal structures and collisionally driven density waves (known as collisional rings) that can extend for tens of kpc from their host galaxy centers. Here we report the discovery of SN 2025adpq, a Type Ia supernova at $z=0.1540$, found within a collisional ring, which we call Pika's Halo, with circumference $\sim$70 kpc that was produced by a major merger between two comparable mass galaxies ($\log