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Scientists unveil largest 3D map of the universe ever

This map shows 11 billion years of the universe's history, with galaxies closest to Earth appearing in purple and blue, and distant galaxies in yellow and red.
This map shows 11 billion years of the universe's history, with galaxies closest to Earth appearing in purple and blue, and distant galaxies in yellow and red.
(Image: © EPFL)

After five years of peering into the deepest reaches of space, researchers have released what they call the "largest three-dimensional map of the universe" ever. No, you cannot see your house.

The mind-boggling map is the result of an ongoing project called the Sloan Digital Sky Survey (SDSS) — an ambitious, international quest to map the expansion of the observable universe, and hopefully solve a few cosmic conundrums in the process. With this newest update, the project has mapped and measured more than 2 million galaxies, stretching from our Milky Way to ancient objects more than 11 billion light-years away.

Related: 11 fascinating facts about our Milky Way

The detailed new map will help astronomers piece together a murky period of the universe's expansion known as "the gap."

"We know both the ancient history of the universe and its recent expansion history fairly well, but there's a troublesome gap in the middle 11 billion years," Kyle Dawson, a cosmologist at the University of Utah and lead researcher of the project,  said in a statement. "For five years, we have worked to fill in that gap."

The gap begins a few billion years after the Big Bang. Scientists are able to measure the rate of the universe's expansion before this thanks to the cosmic microwave background — ancient radiation left over from the infancy of the universe that researchers can still detect; and they can calculate recent expansion by measuring how the distance between Earth and nearby galaxies increases over time. But expansion in the middle period has been little studied because the light of galaxies more than a few hundred million light-years away can be incredibly faint. To fill in the gap, a team of more than 100 scientists from around the world looked at not just distant galaxies, but also bright-burning quasars (extremely luminous objects powered by the hungriest black holes in the cosmos).

Key to this survey is a phenomenon called redshift — a process by which light from the most ancient, distant galaxies is literally stretched by the expansion of the universe, increasing its wavelength and shifting it toward the redder end of the spectrum. As a result of this cosmic color-change, distant light sources appear redder, while those nearer to Earth look bluer (you can see this phenomenon illustrated in the team's maps above).

To calculate the rate of cosmic expansion 11 billion years ago, the team measured the redshift of millions of distant objects along with their velocities — a measurement that shows how much a galaxy is being tugged by the gravity of other matter around it. The team's results, which are described in 23 new studies released on July 20, show that the universe began expanding at an increased rate about 6 billion years ago, following a period of deceleration.

Scientists attribute the universe's expansion to a mysterious force called dark energy, though no one is entirely sure what it is or where it exists. Surveys like this one help scientists better constrain the properties of dark energy, the researchers said, though it remains far from understood. The solution to that conundrum will have to wait for another day … hopefully one not too many billions of years away.

Originally published on Live Science.

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  • rod
    An interesting 3D map presented with differences for the H0 or the Hubble constant too. EBOSS estimated the Hubble constant, 67.4 and 69.0 km/s/Mpc. Others like Freedman noted this difference. "Freedman also notes that the disagreement over the Hubble constant depends to some extent on what methods are used. She herself has done studies using Cepheid variable stars and red giant stars, which give two different results. “I think we still don't know how this issue will be resolved,” she adds. “It is an interesting time in cosmology.”, ref - https://skyandtelescope.org/astronomy-news/new-3d-map-universe-growing-cosmological-debate/
    Using this cosmology calculator, http://www.astro.ucla.edu/~wright/CosmoCalc.html, the Hubble time using z = 67.4 is 14.168E+9 years ago for the age of the universe. Using z=69, Hubble time is 13.84E+9 years ago. There is 3.28E+8 years time difference (delta) between these two values for the Hubble time that could change much in the BB cosmology for timelines, e.g. origin of the CMBR and earlier conditions, e.g. inflation. Freedman et al also report other H0 values, some range up to 82 km/s/Mpc. NASA ADS Abstract, 'The Completed SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Growth rate of structure measurement from cosmic voids', https://ui.adsabs.harvard.edu/abs/2020arXiv200709013A/abstract, July 2020. The arxiv report is attached in this record. The redshift range surveyed is, "eBOSS conducted a 5-year observation program, surveying the large scale structure of the Universe over a redshift range from 0.6 to 3.5." That is some range of redshifts surveyed and SDSS also reported cosmic high-noon for star formation rates too. The early universe according to BB cosmology, created SMBHs, PBHs, star formation rates much faster and higher than anything we see today (e.g. QSO or quasar formations, Population III stars) in astronomy. The universe is running downhill, not uphill and winding down as the universe expands. Processes observed operating today in astronomy are not the same as the early universe in BB cosmology (e.g. inflation, BBN, PBH forming, SMBH forming, quasars forming, Population III stars forming).
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  • Torbjorn Larsson
    Being an integrative cosmological summary based on the baryonic acoustic oscillations and the cosmic microwave background to establish flatness it reinforce the standard model nicely.

    The structure data in the survey strongly fit dark matter evolving according to general relativity. The flatness of space is now 10^-4 – yielding a universe volume at least 100 million times larger than the observable – which is just an order of magnitude from the detection limit.

    Dark energy can be detected at 8 sigma based on accepting flatness, it is constant and yields a current expansion rate at H0 = 68.20 +/- 0,81 km s^-1 Mpc^-1 which likely means no physics (< 72 km s^-1 Mpc^-1 at nearly 3 sigma) and is consistent with simplest anthropic finetuning which they point out as possible and substantially strengthened explanation.

    "Nevertheless, the observed consistency with flat ΛCDM at the higher precision of this work points increasingly towards a pure cosmological constant solution, for example, as would be produced by a vacuum energy finetuned to have a small value. This fine-tuning represents a theoretical difficulty without any agreed-upon resolution and one that may not be resolvable through fundamental physics considerations alone (Weinberg 1989; Brax & Valageas 2019). This difficulty has been substantially sharpened by the observations presented here."
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