"We're seeing the universe as it was when it was newborn," says researcher.
This image shows the oldest light in the universe, called the cosmic microwave background. It combines new details from the Atacama telescope with older data from the Planck satellite.(Photo: ACT Collaboration; ESA / Planck Collaboration)
"When you look at the combination of sharpness, sensitivity, size, and colour information, it's fair to say the images are the most detailed of the background radiation," Sigurd Kirkevold Næss tells sciencenorway.no.
He is a cosmology researcher at the University of Oslo and one of the researchers behind the ACT project.
"Background radiation is the light that lies behind everything else in the universe – behind stars and galaxies. This light has longer wavelengths than our eyes can perceive, and that's why space appears black to us," he says.
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Næss explains that if we could see these longer wavelengths, we would see a glowing fog that lies behind everything else in the universe.
"That's what our telescope sees. We're seeing the universe as it was when it was newborn," he says.
The coloured band in this illustration shows the time period in the universe's history that the new images capture.(Image: Lucy Reading Ikkanda, Simons Foundation)
A clearer look at the beginning
This is not the first time the cosmic background radiation has been observed. In 1964, radio astronomers Arno Penzias and Robert W. Wilson discovered it for the first time, which earned them the Nobel Prize in Physics in 1978.
"Our measurement is the most accurate one to date," cosmology researcher Sigurd Næss says about the new ACT images.(Photo: Private)
The space-based telescope Planck was Europe's first mission to study the cosmic microwave background in 2009.
The new images from ACT now provide higher resolution than what was previously observed by the Planck telescope.
"ACT has five times the resolution of Planck," Sigurd Næss says in a press release.
The ACT images also show how strong and in which direction the earliest light travelled. This is called polarisation.
The polarisation of the background radiation provides information about how the gases in the early universe moved – essentially the first step towards forming stars and galaxies.
Næss points out that the polarisation of the background radiation was not measured for the first time in this study.
"It was first measured by the Degree Angular Scale Interferometer (DASI) in 2002. But the signal is extremely weak, so DASI's data was nearly unusable. Since then, newer and more advanced telescopes have gradually improved the measurements. Our measurement is the most accurate one to date," he says.
In the beginning, the universe was so hot that light could not move freely.
Only after 380,000 years did the temperature drop enough for light to pass through. This is the light that ACT has now measured in detail.
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The new images allow researchers to see small differences in density and movement in the gases that filled the newborn universe.
What looks like clouds of fog are actually areas with more or less gas – like peaks and valleys in a sea of hydrogen and helium.
This image shows the direction in which light from space vibrates – something called polarisation.(Photo: ACT Collaboration; ESA / Planck Collaboration)
Over time, the densest areas were pulled together by gravity, and that's how stars and galaxies were formed.
"By looking back to that time when things were much simpler, we can piece together the story of how our universe evolved to the rich and complex place we find ourselves in today," Jo Dunkley, a professor at Princeton University and lead analyst in the ACT project, says in the press release.
