Astronomers may be getting closer to understanding one of the biggest mysteries in cosmology: dark energy, the unknown force believed to be driving the accelerating expansion of the universe.
Dark energy is thought to account for about 68% of the universe. Despite its enormous influence, scientists still do not know what it is or exactly how it shapes the growth of the cosmos.
Now researchers have identified an unusual supernova in the early Universe that could provide a valuable new clue. The light from this powerful explosion has been traveling toward Earth for more than 10 billion years. The event was exceptionally bright, and its light was further amplified by the gravity of a galaxy along the line of sight, making the distant explosion appear even more luminous.
“No one has found a supernova like this before, and the nature of the system means it may be able to help solve some big problems in astrophysics such as the nature of the force that drives the expansion of the universe,” explains Dr. Daniel Perley, a reader in astrophysics at Liverpool John Moores University.
Gravity Splits the Light Into Multiple Images
A galaxy positioned directly between Earth and the distant supernova plays a crucial role in the discovery. Its gravitational pull bends the light traveling from the explosion toward us.
“We are seeing the light from this distant supernova split into multiple images, what we call ‘gravitationally lensed’,” explains Jacob Wise, a PhD student at the Astrophysics Research Institute, who first recognized the importance of the event.
Light’s varying paths to Earth
“When light is ‘lensed’, the different paths the light follows to get to Earth don’t all have the same length, so light moving along different paths takes variable amounts of time to reach us.”
Because a supernova can shine for several months, astronomers can observe multiple images of the same explosion at once. Each image represents the supernova at a slightly different moment in its evolution because the light traveled along paths of different lengths.
“What’s exciting about that is that the amount of time difference between different images depends on the expansion rate of the universe,” added Dr. Perley.
The research team, working with collaborators at Caltech, Stockholm University, and other institutions around the world, plans to measure these time delays with high precision. Those measurements could reveal how quickly the universe is expanding and provide insight into the force (dark energy) responsible for accelerating that expansion.
A Potential Tie Breaker in the Hubble Tension
Astronomers currently face a major puzzle about the universe’s expansion rate. Different methods produce conflicting values for the Hubble constant, the number used to describe how fast the universe is expanding.
Perley believes observations of this unusual supernova could help resolve the disagreement.
He said: “Studies of afterglow of the Big Bang give one number for the so-called Hubble constant — the measurement of the expansion speed of the universe — while studies of nearby galaxies give a different number. Astronomers are calling this the Hubble Tension. Hence, studies of lensed supernovae could indicate which of these two numbers we should really believe.”
Observatories Around the World Join the Study
The supernova’s brightness allowed astronomers to detect it even from its enormous distance using medium sized ground based telescopes. These included the Zwicky Transient Facility in California and the Liverpool Telescope in La Palma.
(The first telescope to detect the supernova was the Zwicky Transient Facility in California, but it couldn’t see the multiple images. The Liverpool Telescope was the first facility to see the multiple images — and thereby prove it was gravitationally lensed)
The object was later studied in greater detail using some of the world’s most powerful observatories, including the Keck Telescopes in Hawaii, the Hubble Space Telescope, and the James Webb Space Telescope.
Added Jacob: “Our colleagues in Stockholm first noticed the supernova but it was us who spotted that the light had been bent into multiple images.
“All the major observatories in the Northern Hemisphere plus the space-based telescopes have been looking at this but it was the Liverpool Telescope, run from LJMU, that got there first,” beamed Wise.
The study “Discovery of SN 2025wny: A Strongly Gravitationally Lensed Superluminous Supernova at z = 2.01” was published in the journal Astrophysical Letters and authored by Joel Johansson, Daniel A. Perley, Ariel Goobar, Jacob L. Wise, Yu-Jing Qin, Zoë McGrath, Steve Schulze, Cameron Lemon, Anjasha Gangopadhyay, Konstantinos Tsalapatas, and 24 other co-authors.