Research published in Monthly Notices of the Royal Astronomical Society demonstrates that Type Ia supernovae can effectively measure the pace at which the universe expands, challenging previous evidence that questioned its accuracy.
"The data that we examined are indeed holding up against these claims of the demise of Type Ia supernovae as a tool for measuring the universe,” said Daniel Scolnic, an author on the study and a postdoctoral scholar at University of Chicago’s Kavli Institute for Cosmological Physics, in a statement. “We should not be persuaded by these other claims just because they got a lot of attention, though it is important to continue to question and strengthen our fundamental assumptions.”
The theory that the exploding star can be utilized to determine cosmic distance is based on the premise that Type Ia supernovas, unlike other supernovas, explode with about the same brightness every time, likely due to a critical mass limit. The brightness of the light can then be used to determine how far away the star is.
However, this method has been challenged in recent years based on findings that the light given off by Type Ia supernovae are more inconsistent than expected. Previous research concluded that the brightness of these supernovae seems to be in two different subclasses, which could lead to problems when trying to measure distances.
Using data from the Sloan Digital Sky Survey Supernovae Search and the Supernova Legacy Survey, researchers at the University of Chicago and Wayne State University simulated Type Ia supernovae-light curves with a model of two ultraviolet classes and found no evidence for distinct near ultraviolet sub-classes. This conclusion supports a widely held theory that the expansion of the universe is accelerating and such acceleration is attributable to a force known as dark energy.
The new findings are reassuring for researchers who use Type Ia supernovae to gain an increasingly precise understanding of dark energy, said Joshua Frieman, senior staff member at the Fermi National Accelerator Laboratory, who was not involved in the research.
“The impact of this work will be to strengthen our confidence in using Type Ia supernovae as cosmological probes,” he said in a statement.
Study author Scolnic has previously defended the accuracy of Type Ia supernovae for the measurement of the age of the universe.
A 2016 study published in Nature argued that there was marginal evidence for cosmic acceleration from Type Ia supernovae.
The criticism focused on the way Type Ia supernovae are analyzed. When scientists found that distant Type Ia supernovae were fainter than expected, they concluded the universe is expanding at an accelerating rate. That acceleration is explained through dark energy.
The authors of the Nature article revaluated the mathematical tools used to analyze supernovae and argued that Type Ia supernovae do not show dark energy exists in the first place.
Scolnic—along with Adam Riess— who won the Nobel Prize for the discovery of the accelerating universe in 2011—refuted those findings in an article for Scientific American in Oct. 2016, stating that even if the mathematical tools to analyze Type Ia supernovae are used “incorrectly,” there is still a 99.7 percent chance the universe is accelerating.