Universe expansion remained a mystery during the early 1990s. The results obtained from Hubble’s Space Telescope (HST) observations in 1998 confirmed that expansion of universe has been accelerating since the big bang. But no one could explain this acceleration as everyone at first thought that the universe’s expansion might slow down due to the presence of gravity. However, the latest studies might help reveal the mystery behind the universe’s expansion soon.
The standard model of cosmology (SMC) assumes that the universe is primarily made of 3 ingredients which are: dark energy which makes roughly 68% of the universe; the equally mysterious dark matter that makes up to 27% and ordinary matter, which accounts for less than 5% of the Universe’s total mass and energy. This means that we only know about 5% of the universe and the rest is yet to be discovered. Even though we have more findings of dark matter, dark energy still remains mysterious. Dark energy is considered to be an unknown energy that opposes gravitational energy. We don’t know much about dark energy except the fact that it accounts for the largest portion of the universe.
Two years ago, cosmologist Marc Kamionkowski at Johns Hopkins University in Baltimore, Maryland, and his collaborators suggested an extra ingredient for this standard model. They suggested ‘early dark energy’ -a second form of dark energy which would be a sort of fluid that permeated the Universe before withering away within a few hundred thousand years of the Big Bang. Recently cosmologists have found more clues regarding early dark energy which might have existed in the first 300,000 years after the Big Bang. Two separate studies, posted on the arXiv preprint server have detected a tentative first trace of this ‘early dark energy’ in data collected by the Atacama Cosmology Telescope (ACT) in Chile. This data collected between 2013 and 2016 shows the following observations.
Early dark energy would have caused the plasma that emerged from the big bang to cool down much faster. This might have helped in accelerating the universe’s expansion. The early dark energy model shows conflict with the standard energy model. Based on the early dark energy model and ACT data, it would mean that the Universe is now 12.4 billion years old which is about 11% younger than the 13.8 billion years calculated using the standard model. Also, the current expansion would be about 5% faster than the standard model predicts.
“There are a number of reasons to be careful to take this as a discovery of new physics,” Silvia Galli, a cosmologist at the Paris Institute of Astrophysics told Nature. The evidence obtained about early dark energy is not clear enough to state it with high confidence says the authors of both preprints; one posted by the ACT team and the other by an independent team. Silvia Galli warns that the ACT data seem to be inconsistent with calculations by the Planck team, which she was part of. Even though the ACT’s polarization data favours early dark energy, the other major set of data which is a map of CMB(Cosmic Microwave Background) temperatures is unclear with this preference. So, it is very important to crosscheck the results using a south pole telescope to get an affirmation. “If this really is true — if the early Universe really did feature early dark energy — then we should see a strong signal,” Colin Hill, a co-author of the ACT team’s paper who is a cosmologist at Columbia University in New York city told Nature.
Also Read: “A new hunting strategy for dark matter“
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