Astronomers calculate the age of the universe using the Atacama Desert Telescope

High in the Atacama Desert in Chile, miles away from the faint glow of light pollution, the isolated Atacama Cosmological Telescope is in a prime position to search the sky for answers. The last question on his mind? The age of the universe, a cosmic dilemma, can be answered in different ways, depending on how you measure the accelerating expansion of the universe.

Paper recently Published in the Journal of Cosmology and Astrophysics He measured the rate of this expansion, called the Hubble constant, using the National Science Foundation telescope in Chile.

The team found that the Hubble constant is 42 miles per second per megaparsec – that is, for every megaparsec, or 3.26 million light-years, the Universe’s expansion speed increases by 42 miles per second. The number that the international team of astronomers and physicists found, after 730 days of observation that spanned from 2013 to 2016, was roughly the same rate as previously reported by the European Space Agency’s Planck satellite in 2013.

“Now we have an answer where Planck is [Atacama Cosmology Telescope] Agree, “said Simon Ayola, researcher at the Flatiron Institute’s Center for Computational Astrophysics and co-author of the paper. In a press release. “It speaks to the fact that these difficult measurements are reliable.”

There is a big reason why the constant is worth recalculating: There are several methods of measuring the expansion rate of the universe by which the age of the universe can be inferred. You can measure the rate based on stellar objects close to us, such as Cepheid pulsars. You can also measure the expansion by looking at the polarized light of the cosmic microwave background, which is the radiation that can be detected far from the Big Bang, which is what the Atacama team did here. This mysterious light has a variation in its polarization, which enables scientists to measure the distance the light traveled and how long it took. This is why it is important to understand the expansion rate of the universe: it changes the distance the light has traveled, and thus the age of everything.

Polarized image of the Cosmic Microwave Background (CMB).

Polarized image of the Cosmic Microwave Background (CMB).
picture: ACT Collaboration

And herein lies the problem: These two methods of calculating the Hubble constant came up at very different rates –One 2019 study It reached approximately 46 mph per mega-leagues, while … Another of the same year Find a number that divides the difference between the other two. Although the differences may appear small, the changing estimates imply a span of hundreds of millions of years in determining the age of our universe. (The higher the constant, the smaller the universe.)

The Atacama team’s results put the age of the universe at about 13.77 billion years. Our solar system, for comparison, is about 4.57 billion years old, and Homo sapiens It appeared somewhere around 300,000 years ago.

The disparate numbers yet don’t mean either side is necessarily wrong (although the team behind the new paper, which is working with better-resolution images of the cosmic microwave background than their Planck predecessors, has assured that the team’s earlier calculations were solid). What this all definitely means is that we’re missing out on something when it comes to how the expansion of the universe works.

The discrepancy between local and distant measurements of the Hubble constant could mean that “there is a problem with one type of measurement that we do not translate correctly, and therefore there is some type of methodological problem in one measurement or another,” Michael Nimak, an astrophysicist at Cornell University and co-author of the recent paper. “The most exciting possibility is that something is missing in our cosmic model.”

The best may be yet to come for the Atacama Telescope, which debuted in 2007 and has the advantage of being on Earth, making it easier to administer than a space telescope.

“We have yet to extract all the information from the data that we have already collected using the Atacama Cosmology Telescope,” said Steve Choi, an astrophysicist at Cornell University and lead author of the paper. “I hope we learn more exciting physics about our universe through upcoming experiments in Atacama, such as CCAT-prime and the Simons Observatory,” he said, referring to two elevated observatories high in the desert. The telescope in CCAT-prime was renamed the Fred Young Don Millimeter Telescope in September and will look at a plethora of cosmic features, while the Simmons Observatory will focus its observational capabilities on the cosmic microwave background.

Perhaps one of the parties evaluating the age of the universe is ignoring something in their calculations – with many unknowns known in space science, and things not entirely known, it is possible. But according to Nimak, there could easily be something else in the mix that explains the difference in numbers.

“This could be a hint that we are about to discover something new and exciting that we didn’t know before about how our universe works,” he said.

Angelica Johnson

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