Far out cosmology: standard model supported again (Introduction)

by David Turell , Monday, March 04, 2024, 19:18 (54 days ago) @ David Turell

An x-ray study of the universe:

https://www.quantamagazine.org/fresh-x-rays-reveal-a-universe-as-clumpy-as-cosmology-pr...

"Clusters of hundreds or thousands of galaxies sit at the intersections of giant, crisscrossing filaments of matter that form the tapestry of the cosmos. As gravity pulls everything in each galaxy cluster toward its center, the gas that fills the space between the galaxies gets compressed, causing it to heat up and glow in X-rays.

"The eRosita X-ray telescope, lofted into space in 2019, spent more than two years collecting pings of high-energy light from all over the sky. The data has allowed scientists to map the locations and sizes of thousands of galaxy clusters, two-thirds of them previously unknown. In a slew of papers posted online on February 14 that will appear in the journal Astronomy & Astrophysics, the scientists used their initial catalog of clusters to weigh in on several of cosmology’s big questions.

"The results include new estimates of the clumpiness of the cosmos — a much-discussed characteristic of late, as other recent measurements have found it to be unexpectedly smooth — and of the masses of ghostlike particles called neutrinos and of a key property of dark energy, the mysterious repulsive energy that’s speeding up the universe’s expansion.

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"The eRosita observations...bolster the existing picture on all counts. “It’s a remarkable confirmation of the standard model,” said Dragan Huterer, a cosmologist at the University of Michigan who was not involved in the work.

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"One number of interest is the “clumpiness factor” of the universe, S8. An S8 value of zero would represent a vast cosmic nothingness, akin to a flat plain with nary a rock in sight. An S8 value closer to 1 corresponds to steep mountains looming over deep valleys. Scientists have estimated S8 based on measurements of the cosmic microwave background (CMB) — ancient light coming from the early universe. Extrapolating from the cosmos’s initial density variations, researchers expect the current S8 value to be 0.83.

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“'Our result was basically in line with the prediction from the very early time, from the CMB,” said Vittorio Ghirardini, who led the analysis. He and his colleagues calculated an S8 of 0.85.

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"From their map of thousands of clusters, the researchers found that dark energy matches the profile of a cosmological constant, although their measurement has a 10% uncertainty, so an ever-so-slightly varying dark energy density remains possible.

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"These initial papers draw from just the first six months of data. The German group expects to find about four times as many galaxy clusters in the additional 1.5 years of observations, which will allow all these cosmological parameters to be pinpointed with more accuracy. “Cluster cosmology could be the most sensitive probe of cosmology other than the CMB,” said Anja von der Linden, an astrophysicist at Stony Brook University."

Comment: the history of the universe since the Big Bang is quite clear and this article gives it more support.