A research team in Germany has captured images of an exceptionally rare supernova that appears five times in the night sky. This cosmic event could help scientists settle a long-standing debate about how fast the universe is expanding.
Scientists at the Technical University of Munich (TUM) , together with researchers from Ludwig Maximilians University and two Max Planck Institutes, discovered a unique stellar explosion 10 billion light-years away. The supernova, nicknamed SN Winny, is far brighter than typical exploding stars and offers a fresh way to measure the universe’s growth rate.
The supernova stands out because it shows up as five separate images in the sky. This happens due to gravitational lensing, where two foreground galaxies bend and split the supernova’s light as it travels toward Earth. The light takes different paths with slightly different lengths, so it arrives at our telescopes at different times.
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Sherry Suyu, Associate Professor of Observational Cosmology at TUM , leads the research team that found SN Winny. Her group spent six years searching for such an event by studying promising gravitational lenses. In August 2025, they finally got their match. “The chance of finding a superluminous supernova perfectly aligned with a suitable gravitational lens is lower than one in a million,” Suyu explains.
Scientists have two main ways to measure the Hubble constant, which describes the universe’s expansion rate. These methods give different answers, creating what researchers call the Hubble tension. One method measures nearby galaxies step by step, like climbing a ladder. The other studies the cosmic microwave background from the early universe. Both have built-in uncertainties.
By measuring the time delays between the five copies of SN Winny, researchers can calculate the expansion rate directly. The team used the Large Binocular Telescope in Arizona to capture high-resolution color images of the system. The pictures show two lens galaxies in warm tones and five blue copies of the supernova arranged like fireworks.
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This method offers a cleaner measurement than previous approaches. Allan Schweinfurth, a junior researcher at TUM , notes that most lensed supernovae are magnified by complex galaxy clusters that are hard to model. SN Winny is simpler—only two individual galaxies bend its light, making calculations more accurate.
Gravitationally lensed supernovae are extremely rare. Only a handful of such measurements exist. The accuracy also depends on knowing the masses of the lensing galaxies, which control how strongly light bends. The team is now building detailed models of these masses.
This third, independent method could break the deadlock in cosmology. Stefan Taubenberger, who led the supernova identification study , explains that unlike the cosmic distance ladder, this is a one-step method with fewer uncertainties. Astronomers worldwide are now observing SN Winny with ground and space telescopes, hoping their results will help solve the Hubble tension once and for all.
