With data from a magnified, image-multiplexing supernova, a team led by researchers from the University of Minnesota Twin Cities has succeeded in using a first-of-its-kind technique to measure the expansion rate of the universe. Their data provides insight into a long-standing debate in the field and could help scientists determine the age of the universe more accurately and better understand the universe.
The work is divided into two papers published respectively in SciencesIt is one of the best peer-reviewed academic journals in the world the Astrophysical JournalIt is a peer-reviewed scientific journal of astrophysics and astronomy.
In astronomy, there are two exact measurements of the expansion of the universe, also called the “Hubble constant”. One is calculated from close observations of supernovae, and the second uses the “cosmic microwave background,” or radiation that began flowing freely through the universe shortly after the Big Bang.
However, these two measurements differ by about 10 percent, which has caused widespread controversy among physicists and astronomers. If both measurements are accurate, it means that scientists’ current theory about the formation of the universe is incomplete.
“If new, independent measurements confirm this difference between measurements of the Hubble constant, it will become a chink in the armor of our understanding of the universe,” said Patrick Kelly, lead author of both papers and an assistant professor at the university. From the Minnesota School of Physics and Astronomy. “The big question is whether there is a potential problem with one or both measurements. Our research addresses this by using a completely different, independent method of measuring the expansion rate of the universe.”
The University of Minnesota-led team was able to calculate this value using data from a supernova Kelly discovered in 2014 — the first-ever example of a multi-image supernova, which means the telescope took four different images of the same cosmic event. After the discovery, teams around the world predicted that the supernova would re-emerge in a new location in 2015, and the University of Minnesota team caught this additional image.
These multiple images appeared because the supernova was gravitationally captured by a galaxy cluster, a phenomenon in which mass bends and magnifies light. Using the time delays between the appearance of the 2014 and 2015 images, the researchers were able to measure the Hubble constant using a theory developed in 1964 by Norwegian astronomer Sjoor Refsdal that had previously been impossible to apply.
The researchers’ findings don’t completely settle the controversy, Kelly said, but they do provide more insight into the problem and move physicists closer to getting the most accurate measure of the age of the universe.
“Our measurement favors the value from the cosmic microwave background, although it does not strongly contrast with the supernova value,” Kelly said. “If observations of future supernovae imaged by clusters as a result of their gravity yield a similar result, it would identify a problem with the value of the current supernova, or with our understanding of dark matter in the galaxy cluster.”
Using the same data, the researchers found that some current models of dark matter in galaxy clusters were able to explain their observations of the supernovae. This allowed them to determine the most accurate models of the locations of dark matter in the galaxy cluster, a question that has long plagued astronomers.
This research was funded primarily by NASA through the Space Telescope Science Institute and the National Science Foundation.
In addition to Kelly, the team included researchers from the Minnesota Astrophysical Institute at the University of Minnesota. University of South Carolina; University of California, Los Angeles; Stanford University; Swiss Federal Institute of Technology Lausanne; Sorbonne University; University of California, Berkeley; University of Toronto; Rutgers University; University of Copenhagen; Cambridge University ; Kavli Institute for Cosmology; Ben Gurion University of the Negev. University of the Basque Country; University of Cantabria; Consejo Superior de Investigaciones Cientificas (Spanish National Research Council); the observatories of the Carnegie Institution for Science; University of Portsmouth; Durham University; University of California, Santa Barbara; University of Tokyo; Space Telescope Science Institute; Leibniz Institute for Astrophysics Potsdam; University of Michigan; Australian National University; Stony Brook University, Heidelberg University, and Chiba University.