In a landmark achievement poised to reshape our understanding of the cosmos, astronomers from Munich have captured and meticulously modeled an exceptionally rare gravitationally lensed supernova, designated SN 2025wny or affectionately, SN Winny. This discovery heralds a transformative opportunity to refine measurements of the universe’s expansion rate, a cosmic constant that has puzzlingly resisted precise quantification despite nearly a century of scrutiny. SN Winny, located an astounding 10 billion lightyears away, stands out not only because of its exceptional brightness—characteristic of superluminous supernovae—but also because of its spectacular and exceedingly rare appearance: five distinct images formed by the gravitational lensing effect of two foreground galaxies.
Gravitational lensing, a consequence of Einstein’s theory of General Relativity, describes the bending of light around massive objects. Here, two galaxies between SN Winny and Earth act as “cosmic lenses,” warping and splitting the supernova’s light into multiple distinct images. This phenomenon occurs because different light paths through the gravitational field vary slightly in length and curvature, causing the multiple images to arrive at Earth at staggered intervals. By precisely measuring these arrival time delays and comprehensively modeling the mass distributions of the intervening lensing galaxies, researchers can directly infer the Hubble constant—the parameter that quantifies the current rate of cosmic expansion—with unmatched precision and independence from traditional methods.
Traditionally, cosmologists have contended with the so-called “Hubble tension,” a perplexing discrepancy between two principal methodologies for measuring the universe’s expansion. The first, the local distance ladder, infers distances using a calibrated chain of standard candles, involving numerous steps each introducing cumulative uncertainty. The second relies on cosmological models rooted in observations of the cosmic microwave background, the remnant radiation from the Big Bang, extending measurements back to the infant universe. While highly precise, this latter approach depends critically on theoretical assumptions regarding the universe’s evolution, leading to a divergence in results that challenges the standard model of cosmology.
The discovery of SN Winny facilitates a unique, third avenue: a one-step, direct measurement exploiting the robust physics of gravitational lensing. Unlike the local method’s cumulative calibration errors, and the cosmic microwave background’s interpretive assumptions, the time delay technique measures the difference in light travel times through varying curved space-time geometries. This approach holds the promise of dramatically reducing systematic uncertainties and providing an independent benchmark that could resolve longstanding tensions in cosmological parameters.
Given the extreme rarity of gravitationally lensed supernovae—the odds of such events aligning favorably with a suitable lens being less than one in a million—this discovery is a scientific triumph. The team’s painstaking six-year effort curated a catalog of promising gravitational lenses, culminating in the August 2025 serendipitous observation of SN Winny. Situated at a redshift of z=2, this supernova’s detection underscores the synergy of persistent observational campaigns and the advances in high-resolution imaging technologies.
Central to the study’s success was the use of the Large Binocular Telescope (LBT) on Mount Graham, Arizona, featuring two co-mounted 8.4-meter mirrors operating in unison with sophisticated adaptive optics systems. These systems counteract atmospheric distortions, enabling the unprecedented capture of high-resolution color images that reveal unprecedented details of the lensing system. The resulting imagery distinctly delineates the warm-toned foreground galaxies and the five bluish, multiple images of SN Winny—visually resembling cosmic fireworks.
The unusual configuration of five supernova images deviates from the more typical two or four images seen in galaxy-scale lensing systems, offering a uniquely tractable lens model. Junior researchers on the team harnessed these positional datasets to construct a refined mass distribution model for the lensing galaxies. Their analyses indicate smooth and regular mass and light profiles for the lens galaxies, suggesting these galactic neighbors have not interacted via collision despite their projected proximity—a finding that enhances the model’s reliability and boosts confidence in the ensuing cosmological measurements.
Numerical modeling and simulations play a pivotal role in interpreting such lensing events. The time delays between the multiple images of SN Winny depend sensitively on the gravitational potential of the lens galaxies, meaning accurate mass models are essential. By comparing simulated and observed images, researchers can reverse-engineer the gravitational landscape, enabling the calculation of physical distances and expansion rates with remarkable accuracy. These computations integrate aspects of galaxy dynamics, dark matter contributions, and intricate gravitational physics, representing a confluence of observational astronomy, theoretical astrophysics, and computational science.
Beyond its immediate scientific objectives, SN Winny has galvanized an international coalition of astronomers deploying an array of ground-based and space telescopes for multi-wavelength monitoring. These time-critical observations aim to capture the supernova’s evolving brightness and spectra from diverse vantage points, affording a rich dataset to cross-validate models and refine cosmological parameters. The global scientific community eagerly anticipates that resultant data will provide critical insights that may ultimately resolve the infamous Hubble tension and inform the next generation of cosmological theories.
The birth of SN Winny as a new cosmological tool exemplifies the intersection of sophisticated instrumentation, theoretical innovation, and collaborative persistence. Its exploitation could redefine precision cosmology by offering a robust, independent yardstick against which to measure not only the universe’s expansion rate but potentially the distribution and nature of dark matter within lensing galaxies. This research marks a milestone in observational cosmology—a precursor to future endeavors that may increasingly rely on gravitationally lensed transients as fundamental probes of the cosmos.
Such breakthrough science rests on careful instrument calibration and rigorous statistical analyses, ensuring that systematic errors are minimized and interpretations remain valid. The strength of this approach lies in its fundamentally different error sources compared to traditional methods, which makes it well-suited to cross-check and complement existing cosmological measurements. Through refined estimates of the Hubble constant, this pathway holds the promise to substantially inform our understanding of fundamental physics, including the nature of dark energy driving accelerated cosmic expansion.
As this pioneering work progresses, the astronomical community stands poised on the cusp of a paradigm shift. The confluence of observational diligence, advanced modeling techniques, and the serendipity of astrophysical alignments may soon deliver a long-sought resolution to one of cosmology’s most vexing challenges. SN Winny offers not just dazzling images but also — perhaps more importantly — a fresh key to unlock the expansion history of our universe, reconciling disparate measurements and illuminating dark corners of cosmic knowledge.
Subject of Research:
Not explicitly specified in detail beyond cosmological expansion measurement using gravitationally lensed supernovae.
Article Title:
HOLISMOKES XIX: SN 2025wny at z = 2, the first strongly lensed superluminous supernova
News Publication Date:
Not specified in the content provided, though references indicate publications around late 2025 to early 2026.
Web References:
- Professorship for Observational Cosmology at TUM: https://www.ph.nat.tum.de/observational-cosmology/home/
- Observatory of the Ludwig Maximilians University Munich: https://www.physik.lmu.de/observatory/en/
- Max Planck Institute for Astrophysics (MPA): https://www.mpa-garching.mpg.de/
- Max Planck Institute for Extraterrestrial Physics (MPE): https://www.mpe.mpg.de/main
- Excellence Cluster ORIGINS: https://www.origins-cluster.de/en/
References:
- Taubenberger et al., “HOLISMOKES XIX: SN 2025wny at z = 2, the first strongly lensed superluminous supernova”, Astronomy & Astrophysics, December 2025. Preprint: https://arxiv.org/abs/2510.21694
- Ecker, Schweinfurth et al., “HOLISMOKES XX. Lens models of binary lens galaxies with five images of Supernova Winny”, submitted to Astronomy & Astrophysics. Preprint: http://arxiv.org/abs/2602.16620
Image Credits:
Credit: SN Winny Research Group; Dr. Christoph Saulder / MPE; Robert Reich / TUM; Elias Mamuzic / MPA / TUM
Keywords
Supernova, Gravitational Lensing, Cosmology, Hubble Constant, Cosmic Expansion, Time Delay Method, Large Binocular Telescope, High-Resolution Imaging, Dark Matter, Observational Astronomy, Cosmic Distance Ladder, Hubble Tension
