Cosmic expansion might not be accelerating after all

The Danish National Research Foundation’s Niels Bohr professor Subir Sakar from the Niels Bohr Institute in Copenhagen has in a new analysis together with colleagues Alberto Guffanti and Jeppe Trøst Nielsen found that cosmic expansion is occurring on constant rate and without the help of dark energy. These are surprising findings that stands in contrast to the previous Nobel prize-winning work from the 1990s made by Perlmutter, Riess and Schmidt. Inferred from the Hubble diagram of Type Ia supernovae they claimed that the expansion of the universe is accelerating and that the acceleration is driven by an unseen entity called dark energy.

universetThe new discovery of Sakar et al. is however based on a much larger data set than the original study where only 50 of the 740 supernovae were analysed. Sakar et el. analysed a database of 740 type Ia Supernovae which makes it possible to perform solid statistical tests to check whether these standardisable candles indicate cosmic acceleration. Sakar et al. found unexpectedly “that the data are still quite consistent with a constant rate of expansion”.

Subir Sakar explains further: “We analyzed the latest catalogue of 740 Type Ia supernovae – over ten times bigger than the original samples on which the discovery claim was based – and found that the evidence for accelerated expansion is, at most, what physicists call ‘3 sigma’. This is far short of the 5 sigma standard required to claim a discovery of fundamental significance.”

The research is published in Nature journal Scientific Reports