Measuring cosmic distances is challenging, and astronomers rely on several methods and tools – collectively known as “cosmic distance ladders” – to do so. A particularly important tool is Type Ia supernovae, which occur in binary systems in which a star (a white dwarf) consumes matter from a companion (often a red giant) until it reaches the Chandrasekhar limit and collapses under its own mass. As these stars shed their outer layers in a violent explosion, they temporarily outshine anything in the background.
In a recent study, an international team of researchers led by Ariel Goobar from the Oskar Klein Center at Stockholm University discovered an unusual Type Ia supernova, SN Zwicky (SN 2022qmx). In an unusual twist, the team observed an “Einstein Cross,” an unusual phenomenon predicted by Einstein’s general theory of relativity, in which the presence of a gravitational lens in the foreground magnifies light from a distant object. This was a major accomplishment for the team as it involved observing two very rare astronomical events that happened to coincide.
The team consisted of several researchers from the Oskar Klein Center, the Kavli Institute for Cosmology, the Cahill Center for Astrophysics, the Infrared Processing and Analysis Center (IPAC), the Ecole Polytechnique Fédérale de Lausanne (EPFL) and the Center for Interdisciplinary Studies Research Exploration and Research in Astrophysics (CIERA), the Center de Recherche Astrophysique de Lyon, NASA Goddard, the Space Telescope Science Institute (STScI) and several universities. Their research paper describing their findings recently appeared in Nature Astronomy.
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The first detection was made with the Zwicky Transient Facility at the Palomar Observatory in California. This facility is named after Fritz Zwicky, the astronomer who first suggested the existence of dark matter in the 1930s. A few weeks later, the team observed it using adaptive optics (AO) at the WM-Keck Observatory in Maunakea, Hawaii, and the Very Large Telescope (VLT) at the Paranal Observatory in Chile. Based on the observed brightness, Goobar and his colleagues hypothesized that they were observing strong lensing.
These follow-up observations and images taken by the Hubble Space Telescope confirmed this theory and showed that the multi-image lensing came from a foreground galaxy that magnified the supernova by 25 times! This serendipitous discovery offers astronomers numerous opportunities, including the opportunity to study SN Zwicky in more detail and further explore the mysteries of gravitational lensing. As Goobar explained in a press release from Stockholm University:
“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.”
However, the implications go beyond these two phenomena. The study of Type Ia supernovae led astronomers to realize that the cosmos is expanding at an accelerating rate. This discovery earned the discovery team the 2011 Nobel Prize in Physics, which was shared between Saul Perlmutter (The Supernova Cosmology Project) and jointly between Brian P. Schmidt and Adam G. Reiss (The High-z Supernova Search Team). Therefore, observations by SN Zwicky could help astronomers solve the mystery of what is driving this accelerated expansion.
“The extreme magnification of SN Zwicky gives us an unprecedented opportunity to study the properties of distant Type Ia supernova explosions, which we need if we use them to study the nature of dark energy,” said Joel Johansson, postdoctoral researcher at from Stockholm University co-authored the study. In addition, it could also help astronomers to lift the veil over dark matter and provide theories about how the universe will end (e.g. big crunch, big rip, heat death, etc.).
Further Reading: Stockholm University, Natural Astronomy