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Beyond the Milky Way galactic wall

The galaxies in the wall are invisible, but Dr. Pomarède and his colleagues could watch their gravitational effects by compiling data from telescopes around the world.

In the expanding universe, as described by astronomer Edwin Hubble in 1929 and confirmed for almost a century, distant galaxies fly away from us as if they were dots on an inflatable balloon; The farther away they are, the faster they withdraw from us in a relationship called the Hubble Law.

This movement away from Earth causes its light to shift to longer, more reddish wavelengths and lower frequencies, such as when sirens are withdrawn from ambulances. Astronomers use this easy-to-measure “redshift”

; as a proxy for the relative distance in the universe. By measuring the galaxy distances independently, the “Cosmicflows” team, such as Dr. Pomarède and his colleagues call themselves who distinguish movement caused by cosmic expansion from movement caused by gravitational irregularities.

As a result, they found that the galaxies between Earth and the South Pole wall sail away from us a little faster than they should otherwise be pulled out by the huge lump of matter in the wall at about 30 miles per second. And galaxies beyond the wall move outwards more slowly than they should be and are contained by the gravitational resistance of the wall.

An amazing aspect of the wall is how large it is compared to the volume the team has studied: a coherent light filament 1.4 billion light years long packed into a cloud with a radius of maybe 600 million. “In terms of volume, there is hardly room for anything bigger!” Said Dr. Tully in an email. “We should expect our view of the filament to be cut off. that it goes beyond our survey horizon. “

And yet the South Pole wall is cosmologically close. “One might wonder how such a large and not so distant structure went unnoticed,” mused Dr. Pomarède in a statement from his university.

But there is always something more to see in the expanding universe.

On the largest scale, cosmologists should confirm that the universe is expanding smoothly and the galaxies should be evenly distributed. But on smaller, more local scales, the universe appears lumpy and gnarled. Astronomers have found that galaxies, often in their thousands, are collected in huge clouds, known as clusters, and that they are linked together in pointed, luminous chains and filaments to form super clusters that span billions of light years. In between are huge deserts of darkness called cavities.

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