💥 A supernova seen five times could help measure how fast the Universe is expanding

Astronomers have found an exceptionally rare supernova, nicknamed SN Winny, that appears in the sky five separate times.

The reason is gravitational lensing. The supernova is located about 10 billion light-years away, and its light passes near two massive foreground galaxies. Their gravity bends spacetime and sends the light toward Earth along several different paths.

Because each path has a different length, the same explosion reaches us at slightly different times — like five cosmic echoes of one event.

That delay is the key. By measuring the time gaps between the five images, scientists can independently calculate the Hubble constant — the number that describes how fast the Universe is expanding.

This matters because cosmology has a long-standing problem known as the Hubble tension: two major methods give different answers. One uses the cosmic distance ladder in the nearby Universe; the other uses the cosmic microwave background from the early Universe. SN Winny offers a third route, based on lensing geometry and time delays.

The alignment is incredibly rare. According to the researchers, the chance of finding a superluminous supernova perfectly aligned with a suitable gravitational lens is lower than one in a million. The team from TUM, LMU and the Max Planck Institutes spent six years searching for such a system.

https://www.sciencedaily.com/releases/2026/04/260428045603.htm