Two burned-out stars, each about the size of Earth but heavier than the Sun, spiral ever closer until one crashes into the other. The impact triggers a thermonuclear explosion, giving birth to a type Ia supernova. Such flashes serve as cosmic beacons for measuring distances across the universe. Yet the details of their origin remain hotly debated.
In the new study, scientists calculated how the gas cloud glows hundreds of days after the collision. For the first time, they used three-dimensional modeling to account for the cloud's shape and the motion of its material. Earlier calculations were done in one-dimensional approximation, as if the explosion were perfectly spherical. But reality is messier: the cloud is clumpy, with filaments and knots. The 3D model revealed oxygen lines from the remnant of the companion star that the 1D model simply missed.
Comparison with observations gave mixed results. For supernova SN 2021aefx, the model reproduced the visible light well but fell short of nickel emission. For the rarer SN 2022pul, akin to superluminous explosions, there was no match — argon and neon were lacking. The authors suggest that in that case, the companion star was completely destroyed or was more massive, causing more vigorous burning.
The new approach paves the way for distinguishing between explosion scenarios. Future observations with the James Webb Space Telescope, combined with 3D models, will help pin down exactly how a given pair of stars met its end.
A white dwarf the size of Earth is so dense that a teaspoon of its material would weigh as much as an elephant.
In Arthur C. Clarke's novel Rendezvous with Rama, humans explore an alien spacecraft that, according to one theory, might have been built by a civilization that survived a supernova explosion.