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Fresh Twist to Debate Over Universe’s Age From New View of the Oldest Light in the Universe

Atacama Cosmology Telescope

The Atacama Cosmology Telescope measures the oldest mild in the universe, often known as the cosmic microwave background. Using these measurements, scientists can calculate the universe’s age. Credit: Image courtesy of Debra Kellner

Atacama Cosmology Telescope findings recommend the universe is 13.eight billion years previous.

From a mountain excessive in Chile’s Atacama Desert, astronomers with the National Science Foundation’s Atacama Cosmology Telescope have taken a recent have a look at the oldest mild in the universe. Their new observations, plus a bit of cosmic geometry, recommend that the universe is 13.77 billion years previous, give or take 40 million years.

The new estimate matches the one supplied by the commonplace mannequin of the universe and measurements of the identical mild made by the Planck satellite tv for pc, a space-based observatory that ran from 2009-2013.

This provides a recent twist to an ongoing debate in the astrophysics neighborhood, stated Simone Aiola, first writer of one of two new papers on the findings posted July 15 to The hassle is that analysis groups measuring the actions of galaxies have calculated that the universe is tons of of thousands and thousands of years youthful than the Planck crew predicted. That discrepancy instructed {that a} new mannequin for the universe could be wanted, and sparked issues that one of the units of measurements could be incorrect.

“Now we’ve come up with an answer where Planck and the Atacama Cosmology Telescope agree,” stated Aiola, a researcher at the Flatiron Institute’s Center for Computational Astrophysics in New York City. “It speaks to the fact that these difficult measurements are reliable.”

New Picture of Oldest Light

A portion of a brand new image of the oldest mild in the universe taken by the Atacama Cosmology Telescope. This half covers a piece of the sky 50 occasions the moon’s width, representing a area of house 20 billion light-years throughout. The mild, emitted simply 380,000 years after the Big Bang, varies in polarization (represented right here by redder or bluer colours). Astrophysicists used the spacing between these variations to calculate a brand new estimate for the universe’s age. Credit: Image courtesy of ACT Collaboration

The age of the universe additionally reveals how briskly the cosmos is increasing, a quantity referred to as the Hubble fixed. The Atacama measurements recommend a Hubble fixed of 67.6 kilometers per second per megaparsec. This consequence agrees virtually precisely with the earlier estimate of 67.four by the Planck satellite tv for pc crew, nevertheless it’s slower than the 74 inferred from the measurements of galaxies.

“Making this independent measurement is really exciting because there’s a mystery in the field, and this helps us sharpen our understanding of that mystery,” stated Jeff McMahon, an affiliate professor of astronomy and astrophysics at the University of Chicago who led the design of the detectors and different new applied sciences used to make this measurement. “This confirms the ongoing discrepancy. And we still have much more data to analyze, so this is just the beginning.”

Jeff McMahon

Assoc. Prof. Jeff McMahon

The shut settlement between the Atacama Cosmology Telescope and Planck outcomes and the commonplace cosmological mannequin is bittersweet, Aiola stated: “It’s good to know that our model right now is robust, but it would have been nice to see a hint of something new.” Still, the disagreement with the 2019 research of the motions of galaxies maintains the risk that unknown physics could also be at play, he stated.

Like the Planck satellite tv for pc and its earthbound cousin the South Pole Telescope, the Atacama Telescope friends at the afterglow of the Big Bang. This mild, often known as the cosmic microwave background, or CMB, marks a time 380,000 years after the universe’s start, when protons and electrons joined to type the first atoms. Before that point, the cosmos was opaque to mild.

If scientists can estimate how far mild from the CMB traveled to attain Earth, they’ll calculate the universe’s age. That’s simpler stated than accomplished, although. Judging cosmic distances from Earth is difficult. So as an alternative, scientists measure the angle in the sky between two distant objects, with Earth and the two objects forming a cosmic triangle. If scientists additionally know the bodily separation between these objects, they’ll use highschool geometry to estimate the distance of the objects from Earth.

Subtle variations in the CMB’s glow supply anchor factors to type the different two vertices of the triangle. Those variations in temperature and polarization resulted from quantum fluctuations in the early universe that obtained amplified by the increasing universe into areas of various density. (The denser patches would go on to type galaxy clusters.) Scientists have a powerful sufficient understanding of the universe’s early years to know that these variations in the CMB ought to sometimes be spaced out each billion light-years for temperature and half that for polarization. (For scale, our Milky Way galaxy is about 200,000 light-years in diameter.)

The Atacama Cosmology Telescope measured the CMB fluctuations with unprecedented decision and sky protection, taking a more in-depth have a look at the polarization of the mild. “The Planck satellite measured the same light, but by measuring its polarization in higher fidelity, the new picture from Atacama reveals more of the oldest patterns we’ve ever seen,” stated Suzanne Staggs, the telescope’s principal investigator and the Henry deWolf Smyth Professor of Physics at Princeton University.

This measurement was attainable thanks to new expertise designed and constructed by McMahon’s crew. “Basically, we figured out how to make the detectors measure two colors and to pack as many into each camera as possible,” McMahon stated. “Then we developed new lenses out of metamaterials.” (Metamaterials are a kind of materials that’s engineered to produce properties that don’t exist naturally.)

From conception to deployment at the telescope to evaluation, the course of has spanned practically 10 years, McMahon stated. “Working with this amazing team to develop this project all the way from concept sketches to producing results at the forefront of cosmology, has been absolutely fantastic.”

Prof. Wendy Freedman explains a brand new technique for measuring the growth of the universe.

Sara Simon, now at Fermi National Accelerator Laboratory, made important contributions to detector design; UChicago graduate scholar Joey Golec developed strategies to fabricate the metamaterial optics; and UChicago graduate scholar Maya Mallaby-Kay is now working to make the datasets public.

As the Atacama Cosmology Telescope continues making observations, astronomers may have an excellent clearer image of the CMB and a extra actual concept of how way back the cosmos started. The crew can even scour these observations for indicators of physics that doesn’t match the commonplace cosmological mannequin. Such unusual physics may resolve the disagreement between the predictions of the age and growth fee of the universe arising from the measurements of the CMB and the motions of galaxies.

“We’re continuing to observe half the sky from Chile with our telescope,” stated Mark Devlin, the telescope’s deputy director and the Reese W. Flower Professor of Astronomy and Astrophysics at the University of Pennsylvania. “As the precision of both techniques increases, the pressure to resolve the conflict will only grow.”

“I didn’t have a particular preference for any specific value — it was going to be interesting one way or another,” stated Cornell University’s Steve Choi, first writer of the different paper posted to “We find an expansion rate that is right on the estimate by the Planck satellite team. This gives us more confidence in measurements of the universe’s oldest light.”



“The Atacama Cosmology Telescope: DR4 Maps and Cosmological Parameters” by Simone Aiola, et al., 14 July 2020, Astrophysics > Cosmology and Nongalactic Astrophysics.
arXiv: 2007.07288

“The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectra at 98 and 150 GHz” by Steve Okay. Choi, et al., 14 July 2020, Astrophysics > Cosmology and Nongalactic Astrophysics.
arXiv: 2007.07289

The ACT crew is a global collaboration, with scientists from 41 establishments in seven international locations. The telescope is supported by the National Science Foundation and contributions from member establishments.

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