Free Astronomy Magazine September-October 2025

11 SEPTEMBER-OCTOBER 2025 ASTRO PUBLISHING the ‘double-detonation’ mechanism does indeed occur in nature.” The team were able to detect these cal- cium layers (in blue in the image here above) in the supernova remnant SNR 0509-67.5 by observing it with the Multi Unit Spectroscopic Explorer (MUSE) on ESO’s VLT. This provides strong evidence that a Type Ia super- nova can occur before its parent white dwarf reaches a critical mass. Type Ia supernovae are key to our understanding of the Universe. They behave in very consistent ways, and their predictable brightness — no matter how far away they are — helps astronomers to measure dis- tances in space. Using them as a cos- mic measuring tape, astronomers discovered the accelerating expan- sion of the Universe, a discovery that won the Physics Nobel Prize in 2011. Studying how they explode helps us to understand why they have such a predictable brightness. Das also has another motivation to study these explosions. “This tangi- ble evidence of a double-detonation not only contributes towards solving a long-standing mystery, but also offers a visual spectacle,” he says, describing the “beautifully layered structure” that a supernova creates. For him, “revealing the inner work- ings of such a spectacular cosmic ex- plosion is incredibly rewarding.” T his image shows the distribution of calcium in the supernova remnant SNR 0509-67.5. The data were captured with the Multi-Unit Spectroscopic Ex- plorer (MUSE) instrument at ESO’s Very Large Telescope (VLT). The overlaid curves outline two concentric shells of calcium that were ejected in two separate detonations when the star died several hundred years ago. [ESO/P. Das et al.] !