|The microwave sky as seen by Planck. Mottled structure of the CMB, the oldest light in the universe, is displayed in the high-latitude regions of the map. The central band is the plane of our galaxy, the Milky Way. (Photo : ESO)|
In order to solve a mystery, you need to revisit the scene of the crime. In the case of the Big Bang, though, that's a little difficult.
That's why scientists are using cosmic microwave background (CMB) radiation data to look back at the origins of our universe. Now, they've managed to get their furthest look back through time yet, catching a glimpse of the universe a mere 100 to 300,000 years after its birth.
Our knowledge of the Big Bang and the early formation of the universe come almost entirely from measurements of the CMB. These primordial photons were set free when the universe cooled enough for particles of radiation and particles of matter to separate. These measurements reveal the CMB's influence on the growth and development of the large-scale structure we see in the universe today.
Yet actually measuring the CMB is another matter entirely. In order to more precisely examine the universe's origins, the researchers analyzed the latest satellite data from the ESO's Planck mission and NASA's Wilkinson Microwave Anisotropy Probe (WMAP). This pushed CMB measurements to a higher resolution, lower noise and more sky coverage than ever before.
"We found that the standard picture of an early universe, in which radiation domination was followed by matter domination, holds to the level we can test it with the new data, but there are hints that radiation didn't give way to matter exactly as expected," said Eric Linder of the University of Berkeley, in a news release. "There appears to be an excess dash of radiation that is not due to CMB photons."
The researchers found that the CMB photon relic afterglow of the Big Bang was followed mainly by dark matter, as expected. Yet they also found a deviation from the standard that hinted at relativistic particles beyond CMB light. The prime suspects behind these particles are "wild" versions of neutrinos, which are subatomic particles that are the second most populous residents of today's universe. The other suspect is dark energy, the anti-gravitational force that accelerates our universe's expansion.
"Early dark energy is a class of explanations for the origin of cosmic acceleration that arises in some high energy physics models," said Linder. "While conventional dark energy, such as the cosmological constant, are diluted to one part in a billion of total energy density around the time of the CMB's last scattering, early dark energy theories can have 1-to-10 million times more energy density."
In fact, early dark energy could have been the driver that caused the present cosmic acceleration. The latest findings could provide new insight into the origin of cosmic acceleration. In addition, the study reveals a little bit more about the early history of our universe.
The findings are published in the journal Physical Review Letters.