Astronomers at the Atacama Cosmology Telescope (ACT) of the National Science Foundation have reexamined the oldest light in the known Universe. The revised cosmic observations indicate that the Universe is 13.77 billion years old, plus or minus 40 million years old.
The latest age estimate actually coincides with that provided by the standard model of the Universe, using measurements of the same light made by the Planck satellite.
The latest research adds a new twist to an ongoing debate in the astrophysics community, says Dr. Simone Aiola, first author of one of two new articles on the historical study.
Scientists who measured the movements of galaxies in 2019 made headlines around the world after concluding that the Universe is hundreds of millions of years younger than Planck’s team’s prediction.
That discrepancy suggested that a new model for the Universe might be necessary, fueling concerns that one of the sets of measurements might be wrong.
Dr. Aiola, a researcher at the Flatiron Institute’s Center for Computational Astrophysics, said: “We have now found an answer where Planck and ACT agree.
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“It speaks to the fact that these difficult measurements are reliable.”
The age of the Universe also reveals how fast the cosmos is expanding, a number quantified by the Hubble constant.
Data from the Atacama Cosmology Telescope suggests a Hubble constant of 42 miles (67.6 km) per second per megaparsec (approximately 3.26 million light years).
Consequently, this means that an object 1 megaparsec from Earth moves away from the planet at 42 miles per second due to the expansion of the Universe.
This conclusion almost perfectly coincides with the previous estimate of 67.4 km per second per megaparsec by the Planck satellite team.
However, it is slower than the 46 miles (74 km) per second per megaparsec inferred from galaxy measurements.
Steve Choi of Cornell University, first author of the other article, said in a statement: “I had no particular preference for any specific value; It was going to be interesting in one way or another.
“We found an expansion rate that is in Planck’s satellite equipment estimate.
“This gives us more confidence in the measurements of the oldest light in the Universe.”
Professor Erminia Calabrese, Cardiff University School of Physics and Astronomy and lead author of one of the articles, said: “Having worked on extracting the cosmological parameters of ACT and Planck for almost a decade, it was very rewarding see that the two experiments were in agreement.
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“These new ACT results add confidence in our early Universe model and weigh on the controversy with the expansion of the local universe where galaxies seem to be moving faster than ACT and Planck now measure.”
Like the Planck satellite, the Atacama cosmology telescope stars in the glow of the Big Bang.
This cosmic microwave background (CMB) marks a time 380,000 years after the birth of the Universe, when protons and electrons joined together to form the first atoms.
If scientists can estimate how far light from the CMB traveled to reach Earth, they can calculate the age of the Universe.
However, this is easier said than done, since calculating the cosmic distance is notoriously difficult.
Instead, scientists measure the angle in the sky between two distant objects, with Earth and the two objects forming a triangle.
If scientists also understand the physical separation between those objects, they can use high school geometry to estimate the distance of objects from Earth.
Subtle variations in the brightness of the CMB provide anchor points to form the other two vertices of the triangle.
Variations in temperature and polarization resulted from quantum fluctuations in the early Universe amplified by the growing Universe in regions of varying density.
The researchers now have a strong enough understanding of the nascent Universe to realize that these CMB variations must be spaced every billion light years for temperature and half for polarization.
For scale, the Milky Way galaxy is approximately 200,000 light-years across.
Suzanne Staggs, ACT principal investigator and physics professor Henry deWolf Smyth at Princeton University, said: “The Planck satellite measured the same light, but by measuring its polarization more faithfully, the new ACT image reveals more of the patterns older than we have ever seen. “
