Some superluminous supernovae show a bright oxygen imprint in their light and expand rapidly, while others do not. It seemed like different phenomena. But supernova PTF12dam broke the rules: as its brightness grew, its oxygen signature changed, shifting from one type to another.
The solution is simple: all the diversity is just a matter of the temperature of the ejected material at the moment of maximum brightness. The mechanism works like a blowing bubble. At the center is a newborn neutron star the size of a city, spinning hundreds of times per second, with a magnetic field a quadrillion times stronger than Earth's. It pumps energy into the cloud of expelled matter. If the shell is massive, the bubble inflates slowly, cools off quickly, and oxygen in the glow is almost invisible, while the expansion speed drops off gently. Conversely, a light shell yields a rapid rise, a hot peak, and a clear oxygen signal. A simple model, where explosions differ only by the mass of the ejecta, fit the observations perfectly. Moreover, the distribution of material turned out to be uniform, like the film of a soap bubble. Thus, one supernova united what were thought to be different types.
🎯 One such supernova can outshine an entire galaxy, shining brighter than a hundred billion suns.