Rare gravitational lens splits light of distant supernova into four images

Under extraordinary circumstances, large astronomical bodies act as cosmic magnifying glasses. These magnifying glasses also create multiple light paths visible at different positions in the sky. Illustration: Nikki Arendse

The team, led by Ariel Goobar from the Oskar Klein Centre at Stockholm University, discovered an unusual Type Ia supernova, SN Zwicky. Type Ia supernovae play a crucial role in measuring cosmic distances. They were used for the discovery of the accelerated expansion of the universe, leading to the 2011 Nobel prize in physics. The newly discovered supernova stands out due to its extraordinary brightness and configuration of multiple images, a rare phenomenon predicted by Albert Einstein's theory of general relativity.

Montage. Observatory: Caltech/Palomar, Zoom-in: Joel Johansson

Within weeks of detecting the supernova at the Zwicky Transient Facility at Palomar Observatory, the team observed SN Zwicky with the adaptive optics instruments on the W. M. Keck Observatory atop Maunakea, Hawaiʻi, and the Very Large Telescopes in Chile. The Keck Observatory observations resolved the multiple images, confirming the strong lensing hypothesis behind the unusual supernova brightness. The four images of SN Zwicky were also observed with NASA’s Hubble Space Telescope.

Large astronomical bodies act as cosmic magnifying glasses

The multiply-imaged lensing effect observed in SN Zwicky is the result of the gravitational field exerted by a foreground galaxy acting as a gravitational lens. Under extraordinary circumstances, large astronomical bodies act as cosmic magnifying glasses. These magnifying glasses also create multiple light paths visible at different positions in the sky. Observing the multiple images not only reveals details about the strongly lensed supernova, it also offers a unique opportunity to explore the properties of the foreground galaxy that causes the deflection of light. This could teach astronomers more about the inner cores of galaxies and dark matter. Lensed supernovae are also very promising tools to refine models describing the expansion of the universe.

New avenues for investigating gravitational lensing

As scientists continue to unravel the complexities of the universe, the discovery of SN Zwicky's multiply-imaged lensing presents new avenues for investigating gravitational lensing phenomena and their implications for cosmology. This is an important step towards unlocking the mysteries of dark matter, dark energy, and the ultimate fate of our cosmos. “The extreme magnification of SN Zwicky gives us an unprecedented chance to study the properties of distant Type Ia supernova explosions, which we need when we use them to explore the nature of dark energy,“ says Joel Johansson, a postdoctoral fellow at Stockholm University and a co-author on the study.

Researchers at Oskar Klein Centre and Department of Physics, Stockholm University working with the study on SN Zwicky. From left Edvard Mörtsell, Steve Schulze, Joel Johansson, Ana Sagués Carracedo, Ariel Goobar and Nikki Arendse.

Professor Ariel Goobar, the project's principal investigator and the director of the Oskar Klein Centre at Stockholm University, expressed his enthusiasm for this significant finding: "The discovery of SN Zwicky not only showcases the remarkable capabilities of modern astronomical instruments but also represents a significant step forward in our quest to understand the fundamental forces shaping our universe."

The team's findings have been published in Nature Astronomy, in a paper titled "Uncovering a population of gravitational lens galaxies with magnified standard candle SN Zwicky". The publication provides a comprehensive analysis of SN Zwicky, including imaging and spectroscopic data collected from telescopes around the world. 

Institutions including the California Institute of Technology – the leading institution behind the Bright Transient Survey where SN Zwicky was found, University of Cambridge, Liverpool John Moores University, University of Maryland, NASA Goddard Space Flight Center, University of Washington, University of California, Berkeley, University of Portsmouth, Ecole Polytechnique Fédérale de Lausanne, Northwestern University, Humboldt-Universitat zu Berlin, Space Telescope Science Institute, Université de Lyon, CNRS-IN2P3 in France, University of Texas at Austin, and Konkoly Observatory have also contributed to this groundbreaking research.

Researchers at Stockholm University involved in the work are Edvard Mörtsell, Steve Schulze, Joel Johansson, Ana Sagués Carracedo, Ariel Goobar, Nikki Arendse and Remy Joseph from the Department of Physics and Jesper Sollerman from the Department of Astronomy.

Video: Explaining supernova Zwicky with watercolours. (Oskar Klein Centre YouTube)