In 1998, scientists made a discovery that suggests the universe is expanding at an accelerating rate, a find that earned three astronomers the Nobel Prize in Physics in 2011.

The conclusions of this study were based on analysis of data of Type Ia supernovae. The find became a widely accepted idea. It posited that the universe does not expand at a constant rate and that its growth seems to accelerate over time as it gets older, something that is being attributed to an extra energy.

The theory suggests that the so-called dark energy, which is being accounted for almost 70 percent of of all energy in the observable universe, drives this accelerating expansion.

New research conducted by researchers from the Oxford University, however, raises question to this widely accepted idea.

Using data from a catalogue of 740 Type Ia supernovae, Subir Sarkar of Oxford University and colleagues found evidence that the universe is accelerating at a constant rate. Since this rate of expansion is constant, no dark energy would have to be added to accelerate the process — a theory that reflects the model of steady expansion, which was also widely accepted prior to the presentation of the dark energy hypothesis.

Sarkar and colleagues said that the statistical techniques that were used by the original team of researchers were based on a model that was devised in the 1930s that cannot be reliably applied to the growing dataset of supernova.

"There exists now a much bigger database of supernovae so we can perform rigorous statistical tests to check whether these 'standardisable candles' indeed indicate cosmic acceleration," the researchers wrote in their study, which was published in the Nature journal Scientific Reports on Oct. 21.

"Taking account of the empirical procedure by which corrections are made to their absolute magnitudes to allow for the varying shape of the light curve and extinction by dust, we find, rather surprisingly, that the data are still quite consistent with a constant rate of expansion."

Other evidences support the theory of dark energy such as the data on cosmic microwave background, the faint afterglow of the Big Bang, but the researchers said these studies are also flawed.

"All of these tests are indirect, carried out in the framework of an assumed model, and the cosmic microwave background is not directly affected by dark energy," Sarkar said.

While the new study raises question on the existence of dark energy, its results do not necessarily serve as a deathblow to the theory.

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