Astronomers Unveil Revolutionary Method to Measure Universe's Expansion Using Lensed Supernovae

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Astronomers Unveil Revolutionary Method to Measure Universe's Expansion Using Lensed Supernovae

In a significant leap for cosmology, an international consortium of astronomers has devised a groundbreaking new method to precisely measure the rate at which our Universe is expanding. This innovative technique leverages the extremely rare phenomenon of gravitationally lensed superluminous supernovae, offering a direct and potentially more accurate path to determining the Hubble-Lemaitre Constant and addressing one of the most persistent mysteries in astrophysics: the Hubble Tension.

Superluminous supernovae, stellar explosions of extraordinary brightness, serve as crucial "standard candles" for astronomers, allowing them to gauge immense cosmic distances across billions of light-years. These celestial beacons are fundamental to the Cosmic Distance Ladder, a cornerstone method for mapping the vastness of space. However, their utility typically involves inferring distances sequentially, a process prone to accumulating small errors.

The breakthrough came with the observation of a superluminous supernova, officially designated SN 2025wny and affectionately nicknamed "SN Winny." Discovered a staggering 10 billion light-years away, SN Winny was not only exceptionally bright but also exhibited an unprecedented characteristic: its light was bent and magnified by two foreground galaxies, creating five distinct images of the same explosion in the night sky. This spectacular display, akin to cosmic fireworks, was captured by the Large Binocular Telescope (LBT) in Arizona, a collaborative effort involving researchers from institutions like the Technical University of Munich (TUM), the Max Planck Institute for Astrophysics (MPG), and the Harvard & Smithsonian Center for Astrophysics (CfA), among many others globally.

Gravitational lensing, a phenomenon predicted by Albert Einstein, occurs when massive objects like galaxies or galaxy clusters warp spacetime, bending the path of light from more distant sources. In the case of SN Winny, the light took different paths around the two lensing galaxies, resulting in varying travel times to Earth. By meticulously measuring these time delays between the arrival of the multiple images, the research team was able to directly calculate the Hubble-Lemaitre Constant – the precise rate of the Universe's expansion. This paper describing their observations has been accepted for publication in Astronomy & Astrophysics.

Professor Sherry Suyu, Associate Professor of Observational Cosmology at TUM and a Fellow at the Max Planck Institute for Astrophysics, highlighted the rarity and significance of the discovery. "We nicknamed this supernova SN Winny," she stated in an MPG press release. "It is an extremely rare event that could play a key role in improving our understanding of the cosmos. The chance of finding a superluminous supernova perfectly aligned with a suitable gravitational lens is lower than one in a million." The team dedicated six years to compiling a list of promising gravitational lenses, with SN Winny serendipitously matching one in August 2025.

What makes SN Winny particularly valuable is the relative simplicity of its lensing system. Unlike most previous lensed supernovae, which were magnified by complex galaxy clusters, SN Winny was lensed by just two individual galaxies. Junior researcher Allan Schweinfurth from TUM explained, "We find overall smooth and regular light and mass distributions for these galaxies, suggesting that they have not yet collided in the past despite their close apparent proximity. The overall simplicity of the system offers an exciting opportunity to measure the Universe’s expansion rate with high accuracy." This simplicity allowed junior researchers Allan Schweinfurth and Leon Ecker (LMU) to build the first model of the lens mass distribution using the positions of all five images.

This novel methodology offers a promising avenue to address the Hubble Tension, a long-standing cosmological conundrum where measurements of the Universe's expansion rate diverge significantly depending on the method used. Traditionally, scientists rely on two primary approaches: the local Cosmic Distance Ladder, which builds up distances step-by-step from nearby objects to distant supernovae, and measurements derived from the Cosmic Microwave Background (CMB), which extrapolates the expansion rate from the early Universe's relic radiation. Both methods, while highly precise within their frameworks, yield different values for the Hubble-Lemaitre Constant, leading to a persistent disagreement that challenges our fundamental understanding of cosmic evolution.

The lensed supernova technique presents a "one-step" alternative, circumventing the cumulative errors inherent in the Cosmic Distance Ladder and the model-dependent assumptions of CMB measurements. Stefan Taubenberger, a leading member of Professor Suyu’s team and first author on their study, emphasized this advantage: “Unlike the cosmic distance ladder, this is a one-step method, with fewer and completely different sources of systematic uncertainties.” By directly calculating the mass distribution of the lensing galaxies, scientists can derive the Hubble-Lemaitre Constant with a high degree of independence.

Astronomers worldwide are now intensely observing SN Winny using both ground-based and space-based telescopes, eager to gather more data and refine these measurements. The insights garnered from this extraordinary event and the new methodology it enables could provide the crucial evidence needed to reconcile the disparate expansion rates, ultimately leading to a more complete and coherent picture of our Universe's past, present, and future.

Ekhbary News Agency