Scientists have discovered a rare gravitationally lensed supernova, ‘SN Zwicky’, which provides unique insight into the cores of galaxies, dark matter and the mechanics of the universe’s expansion. This discovery uses gravitational lensing, a phenomenon that magnifies celestial objects, according to Einstein’s theory of relativity.
Researchers are gaining insight into how the universe is expanding thanks to gravitational lensing, a natural phenomenon that distorts the space around galaxies and visually magnifies celestial objects.
According to Einstein’s general theory of relativity, time and space are fused together into a quantity known as spacetime. The theory suggests that massive objects, such as a galaxy or galaxy clusters, can cause space-time to warp. Gravitational lensing is a rare but still visible example of Einstein’s theory in action; the mass of a large celestial body can significantly bend light as it travels through space-time, much like a magnifying lens. When light from a more distant light source passes through this lens, scientists can use the resulting visual distortions to see objects that would otherwise be too far away and too faint to see.
An international team of scientists, including University of Maryland astronomer Igor Andreoni, recently discovered an extremely rare supernova with gravitational lensing, which the team named “SN Zwicky.” Located more than 4 billion light-years away, the supernova is magnified almost 25 times by a foreground galaxy acting as a lens. The discovery provides a unique opportunity for astronomers to learn more about the inner cores of galaxies, dark matter and the mechanics behind the expansion of the universe. The researchers published their findings – including a comprehensive analysis, spectroscopic data and images of SN Zwicky – in the journal Natural astronomy on June 12, 2023
Zwicky supernova zoom: starting from a small section of the Palomar ZTF camera, one of 64 ‘quadrants’ each containing tens of thousands of stars and galaxies, the zoom takes us to detailed studies carried out with the larger and sharper VLT telescopes and Keck in Chile and Hawaii respectively. The best-resolution Keck images show the four nearly identical “copies” of the Zwicky supernova. The multiple images arise due to the distortion of space caused by a foreground galaxy, which is also visible in the center and roughly midway between the supernova explosion site and Earth. Credit: J. Johansson
“The discovery of SN Zwicky not only demonstrates 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,” said the paper’s lead author Ariel Gubar, who is also director of the Center for Oscar Klein at Stockholm University.
Originally discovered at the Zwicky Transient Facility (ZTF), SN Zwicky was quickly flagged as an object of interest due to its unusual brightness. Then, using the WM Keck Observatory’s Adaptive Optics Instruments, the Very Large Telescopes and NASA’s Hubble Space Telescope, the team observed four images of SN Zwicky taken from different positions in the sky and confirmed that gravitational lensing is behind the supernova’s extraordinary emission.
SN Cviki. Credit: Joel Johansson, Stockholm University
According to Andreoni, who is a postdoctoral fellow in UMD’s Department of Astronomy and NASAGoddard Space Flight Center, supernovae like SN Zwicky play a crucial role in helping scientists measure cosmic distances.
“Not only is SN Zwicky magnified by gravitational lensing, it also belongs to a class of supernovae that we call ‘standard candles’ because we can use their well-known luminosities to determine the distance in space,” Andreoni explained. “When the light source is further away, the light is weaker – just like seeing candles in a dark room. We can compare two light sources this way and get an independent measure of distance without having to actually study the galaxy itself.
In addition to being useful as a metric for cosmic distance, SN Zwicky also opens up new avenues of inquiry for scientists studying the properties of galaxies, including dark matter (which is matter that does not absorb, reflect, or emit light, but makes up the bulk of matter in the universe). Researchers also believe that lensed supernovae like SN Zwicky could prove to be very promising tools for studying dark energy (a mysterious force that counteracts gravity and drives the accelerated expansion of the universe) and refining current models describing the expansion of the universe, including the calculation of the Hubble constant – a value that describes how fast the universe is expanding.
For Andreoni, who is preparing to open the Vera Rubin Observatory in Chile, the team’s success in identifying and analyzing SN Zwicky is just the beginning. Now still under construction, the new observatory is expected to become fully operational in 2024 and build on the team’s findings as it takes multiple images of the entire visible sky to look for other supernovae and asteroids. Andreoni believes that the “big picture” tactics used to find SN Zwicky will continue to help scientists collect large volumes of data about celestial events in the sky.
“This discovery paves the way for finding more such rare lensed supernovae in future large-scale surveys that will help us study transient astronomical events such as supernovae and gamma-ray bursts,” Andreoni said. “We look forward to more unexpected discoveries using broad, untargeted optical surveys of the sky like the one that helped us identify SN Zwicky.” With this approach, we will be able to probe the transient sky with unprecedented depth.
To learn more about how gravitational lensing works, please see the short animation below:
Massive objects such as galaxies or galaxy clusters warp the spacetime around them in such a way that they can create multiple images of background objects. This effect is called strong gravitational lensing. Credit: ESA/Hubble, NASAThe paper “Revealing a population of gravitationally lensed galaxies with the SN Zwicky magnified standard candle” was published on 12 June 2023 in Natural astronomy.
Reference: “Revealing a population of gravitationally lensed galaxies with an upscaled SN Zwicky standard candle” by Ariel Gubar, Joel Johansson, Steve Schulze, Niki Arendse, Ana Saguez Caracedo, Suhail Dhawan, Edward Moertsel, Christopher Fremling, Lin Yan, Daniel Perley, Jesper Sollerman, Rémy Joseph, K-Ryan Hinds, William Meynardie, Igor Andreoni, Eric Bellm, Josh Bloom, Thomas E. Collett, Andrew Drake, Matthew Graham, Mansi Kasliwal, Shri R. Kulkarni, Cameron Lemon, Adam A. Miller, James D. Neal, Jakob Nordin, Justin Pierrel, Johan Richard, Reid Riddle, Mikael Rigolt, Ben Rusholm, Yashvi Sharma, Robert Stein, Gabriel Stewart, Alice Townsend, Joseph Vinko, J. Craig Wheeler and Avery Wald, 12 Jun 2023, Natural astronomy.
DOI: 10.1038/s41550-023-01981-3
The research was supported by the National Science Foundation (grant nos. AST-2034437 and 1106171), the Knuth and Alice Wallenberg Foundation (under Dnr KAW 2018.0067 and research project grant “Understanding the Dynamic Universe”), the Swedish Research Council (project no. 2016 -06012 and Contract Nos. 2020-03444 and 2020-03384), the European Research Council (Grant No. 759194-USNAC), the European Organization for Astronomical Research in the Southern Hemisphere, and the UK Science and Technology Facilities Council. This story does not necessarily reflect the views of these organizations.