By observing the brightness of distant dying stars, astronomers have long come to believe that the expansion of the universe is accelerating. In fact, that apparent reality is deeply built into cosmological models: a mysterious force that influences the universe on the largest scales, dubbed dark energy, is believed to explain the acceleration.
However, not everybody agrees with this widely accepted scientific consensus. In a controversial new paper, published in the journal Monthly Notices of the Royal Astronomical Society, a team led by Yonsei University astronomer Young-Wook Lee argues that once we take into consideration the age of these dying stars, the expansion acceleration suddenly disappears.
In fact, Lee and his colleagues suggest the expansion started to decelerate 1.5 billion years ago, and could even reverse entirely in the future, resulting in a “big crunch” that effectively turns the concept of a Big Bang on its head, as New Scientist reports.
It’s a contentious new take on cosmology that’s bound to draw plenty of skepticism from the scientific community. If confirmed, however, it would have colossal implications for our understanding of the universe — and, ultimately, its fate.
For decades, scientists have posited that type Ia supernovae, which result from white dwarf stars exploding in a binary system, can stand in as “standard candles” to allow us to measure the cosmos. That’s because scientists believe they are all equally bright. By using the inverse-square law, scientists have measured the distance to these exploded remnants, resulting in the consensus that the universe’s expansion is accelerating.
Simply put, the dimmer the supernova appears in observations, the further away it’s believed to be from us.
However, Lee argues that this conclusion is wrong and that the brightness isn’t actually the same for each of these dying stars. The team argues that once you consider the age of each of these supernovae, the perceived acceleration goes away.
The team used a sample of 300 galaxies to model the brightness of type Ia supernovae, and found that their dimming arose from “stellar astrophysics effects,” and not just distance.
“Our study shows that the universe has already entered a phase of decelerated expansion at the present epoch and that dark energy evolves with time much more rapidly than previously thought,” Lee said in a statement. “If these results are confirmed, it would mark a major paradigm shift in cosmology since the discovery of dark energy 27 years ago.”
Not everybody is convinced of the findings. Space Telescope Science Institute physicist Adam Riess, who received the Nobel Prize in physics for the discovery of dark energy through the measurement of type Ia supernovae in 2011, told New Scientist that it’s not easy to determine the age of these dying stars since there’s a lot we still don’t know about their evolution.
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