Astronomers have tracked the streams of galaxies across 700 million light years

(ORDO NEWS) — Everything in our universe is moving, but the time frame needed to observe movement often far exceeds a human lifetime.

In a major study, a team of astronomers from the Institute of Astronomy at the University of Hawaii (IfA), the University of Maryland and the University of Paris-Saclay traced the movement of 10,000 galaxies and galaxy clusters, the dominant masses of matter, within 350 million light-years. Their movements have been traced over 11.5 billion years, from the origin of galaxies when the universe was only 1.5 billion years old, to today.

Using a mathematical method of numerical operations, the team calculated paths based on the current brightness and position of the galaxies, as well as their current movement away from us.

Astronomers have taken into account the physics of the Big Bang theory, including the idea that galaxies initially start to expand apart from each other almost exactly at the rate of Hubble’s expansion. Over time, gravity changes the motion of galaxies so that they not only move apart as the universe expands, but also contract into filaments, walls, and clusters, and devastate other areas that are now voids.

Over eons of time, galaxies typically deviate from the rate of pure Hubble expansion by millions of light years per billion years. In areas of high density, the orbits of galaxies can become quite complex and involve collisions and mergers.

Astronomers have tracked the streams of galaxies across 700 million light years 2 1

Fig.1. Laniakea supercluster superimposed on orbits and mass density surfaces. Credit: University of Hawaii.

“We draw attention to the detailed history of the formation of large-scale mass structures in the universe by reverse engineering the gravitational interactions that created them,” said Ed Shaya, an associate researcher at the University of Maryland.

There are some particularly interesting large areas of high density of matter and galaxies that astronomers are exploring. One of them, the “Great Attractor”, is the core of the Laniakea Supercluster, the vast supercluster of galaxies that contains our own Milky Way. The galaxies can be seen streaming towards a location inside a nest of four rich clusters.

The second exciting region is in the nearby Perseus-Pisces filament of galaxies, which spans nearly a billion light-years and is one of the largest known structures in the universe. The surroundings of the Virgo Cluster, the nearest large cluster, are also visible and can be studied in detail because they are nearby.

Astronomers have tracked the streams of galaxies across 700 million light years 3

Fig.2. A slice of the local universe showing the orbits followed by galaxies highlighted in white and the contours of areas of high density marked in shades of yellow-orange. The Milky Way (center), the Core of the Great Attractor of the Laniakea supercluster (left), Perseus-Pisces (right). Credit: University of Hawaii.

“For more than 30 years, astronomers have considered the Great Attractor to be the main source of gravity that causes the entire region near us to move at a high peculiar velocity relative to uniform cosmic expansion, but the nature of this source is unclear,” said R. Brent Tully, astronomer at IfA, co-author research. “Our orbital reconstructions provide the first clear view of this previously enigmatic region.”

Throughout space, orbits can be projected into the future. The accelerating expansion of the universe dominates the overall picture, causing most galaxies to drift apart. But some consolidation and mergers will continue in localized regions.


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