Supernova ‘Winny’ Seen Five Times Reveals Clues to Universe’s Expansion

By VirentaNews Staff — April 29, 2026

In a cosmic rarity, astronomers have observed a single supernova explosion appearing five distinct times across the sky—a phenomenon so rare it’s been likened to seeing a firework burst simultaneously in multiple locations. Dubbed SN Winny, this superluminous supernova lies 10 billion light-years from Earth and is magnified and multiplied by the gravitational pull of two foreground galaxies. This effect, known as strong gravitational lensing, bends and splits the supernova’s light into multiple paths, creating a unique opportunity to measure the Hubble constant—the rate at which the universe is expanding—with extraordinary precision. Such events occur roughly once in every million supernovae, making SN Winny a goldmine for cosmologists seeking to resolve one of the most persistent puzzles in modern astrophysics.

The Expanding Universe Conundrum

The rate at which the universe expands—quantified by the Hubble constant—has been a cornerstone of cosmology since Edwin Hubble’s groundbreaking observations in the 1920s. Yet nearly a century later, scientists still cannot agree on its exact value. Measurements based on the cosmic microwave background (CMB), the afterglow of the Big Bang observed by the Planck satellite, suggest a slower expansion rate of about 67 kilometers per second per megaparsec. In contrast, observations of nearby supernovae and Cepheid variables yield a faster rate of around 73. This discrepancy, known as the ‘Hubble tension,’ hints at either unaccounted-for errors in measurement or the presence of unknown physics, such as new forms of dark energy or modified gravity. SN Winny’s fivefold appearance offers a rare, independent method to calculate the Hubble constant, potentially bridging the gap between these conflicting measurements.

A Once-in-a-Million Cosmic Alignment

SN Winny was first detected by the Zwicky Transient Facility in California and later confirmed with observations from the Hubble Space Telescope and the W. M. Keck Observatory. What sets it apart is its remarkable lensing configuration: the light from the distant supernova passes through a galaxy cluster containing two massive galaxies aligned almost perfectly between Earth and the source. Their combined gravity warps spacetime so dramatically that the supernova’s light splits into four distinct images arranged in a cross-like pattern—known as an Einstein cross—with a fifth, fainter image appearing slightly farther out. Each image shows the supernova at a slightly different moment in time because the light rays travel different distances and through varying gravitational potentials. By monitoring the brightness changes across all five images, astronomers can measure these time delays with high accuracy.

Measuring Cosmic Delays for Precision Cosmology

The key to unlocking the Hubble constant from SN Winny lies in these time delays. As light from the supernova explosion takes different paths around the lensing galaxies, some routes are longer than others, causing the same event to appear days or even weeks apart in each image. By modeling the mass distribution of the lensing galaxies and measuring the arrival times of the supernova’s brightness peaks, researchers can calculate the relative light travel times and, crucially, infer the absolute distance to the supernova. This distance, combined with the redshift of its host galaxy, allows for a direct determination of the Hubble constant. Unlike other methods that rely on a ‘cosmic distance ladder’ built from multiple calibration steps, this technique—called time-delay cosmography—is self-contained and less prone to cumulative errors. A similar approach was used with the gravitationally lensed supernova Refsdal, but SN Winny’s five images provide more observational constraints and greater statistical power.

Implications for Fundamental Physics

If the Hubble constant derived from SN Winny aligns more closely with the CMB-based value, it could reinforce the standard cosmological model—Lambda CDM—but raise deeper questions about local measurements. Conversely, if it supports the higher local value, it may lend credence to theories proposing new physics beyond the standard model, such as early dark energy or interacting dark matter. The precision offered by five images could reduce uncertainty to under 2%, a significant improvement over current estimates. Moreover, SN Winny’s extreme distance offers a probe into the universe’s expansion during an earlier epoch, helping scientists understand whether the Hubble tension is due to systematic errors or an evolving expansion rate over time.

Expert Perspectives

“This is a dream case for time-delay cosmography,” said Dr. Simon Birrer, a cosmologist at UCLA involved in the analysis. “Five images give us redundancy and cross-checks that we’ve never had before.” However, some scientists urge caution. Dr. Wendy Freedman, an astronomer at the University of Chicago known for her work on the Hubble constant, noted, “Gravitational lensing models depend heavily on our understanding of dark matter distribution, which still carries uncertainties.” While optimistic, experts agree that SN Winny alone won’t resolve the Hubble tension—but it could be a pivotal piece in the puzzle.

Looking ahead, astronomers will continue monitoring SN Winny’s fading light over the coming months. Upcoming observatories like the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope are expected to discover dozens of similarly lensed supernovae, opening a new era of precision cosmology. As data accumulates, the mystery of the universe’s true speed may finally be within reach—not from one observation, but from a constellation of cosmic echoes lighting up the sky.

Source: ScienceDaily