Scientists have known for almost a century that the universe is expanding, but we still don’t fully understand the rate of that expansion. Recently, researchers from several institutions in Germany discovered a rare type of supernova that could help us measure it more accurately.
This supernova, dubbed SN Winny, is about 10 billion light-years away and stands out because it is far brighter than typical supernovae. What makes it even more fascinating is that it appears in the sky as five separate points of light. This unusual sight is due to gravitational lensing; two galaxies in the foreground are bending the supernova’s light, creating multiple images.
As light from SN Winny travels to Earth, the gravity of these nearby galaxies warps its path. Each image reaches us at different times because the light takes slightly different routes. By measuring these time delays, scientists can calculate the universe’s expansion rate, known as the Hubble constant.
Sherry Suyu, an associate professor in observational cosmology at the Technical University of Munich, explains, “The chance of finding a superluminous supernova perfectly aligned with a suitable gravitational lens is incredibly low.” After a six-year search, they finally found SN Winny in August 2025.
A Unique Cosmic Setup
Gravitationally lensed supernovae are rare, so their measurements are limited. How well scientists understand the masses of the galaxies bending the light is crucial, as it impacts the lensing effect.
To enhance their measurements, researchers used the Large Binocular Telescope in Arizona, which captured a high-resolution image of this cosmic phenomenon. The image clearly shows the two galaxies and the five images of SN Winny, which is unusual since similar systems typically yield only two or four images.
By studying this arrangement, Allan Schweinfurth and Leon Ecker created a model of how mass is distributed in these galaxies, revealing a simpler and more stable system than previously seen. Allan notes, “Most lensed supernovae involve complex galaxy clusters. SN Winny is lensed by just two individual galaxies, providing a clearer opportunity to measure the universe’s expansion rate.”
The Hubble Tension
Currently, astronomers use two main methods to measure the Hubble constant, but they often yield conflicting results, a situation known as the “Hubble tension.”
One method, known as the cosmic distance ladder, involves measuring distances to nearby galaxies and building from there. Because it depends on many steps, small errors can accumulate, leading to uncertain results.
The second method examines the cosmic microwave background, the faint radiation from the Big Bang, to estimate the current expansion rate. While precise, it relies on assumptions about the universe’s early history, which are still debated.
A Promising New Approach
SN Winny introduces a third method involving measurements from lensed supernovae. Stefan Taubenberger, a key team member, details this approach: “We can directly determine the Hubble constant by measuring the time delays of the multiple images of SN Winny and knowing the lensing galaxies’ mass.” This method has fewer uncertainties and could bridge the gap between existing measurement approaches.
Astronomers worldwide are continuing to observe SN Winny with both ground-based and space telescopes. These new insights may resolve the long-standing debate over how fast the universe is truly expanding.
This discovery continues to stir excitement in the scientific community and highlights how advancements in technology—like high-resolution telescopes—can lead to significant breakthroughs in our understanding of the cosmos.
For further details, you can read more at sources like NASA and the European Space Agency.
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Space Exploration; Space Telescopes; Galaxies; NASA; Black Holes; Astrophysics; Asteroids, Comets and Meteors; Cosmology
