This article is from the May 2021 issue of Sciences et Avenir – La Research n ° 891.

A “river” of galaxies on one side and a vacuum bubble on the other: this would be the farthest distance of our galaxy.

The Milky Way is a community of more than 60 galaxies

To understand how astronomers were able to draw this landscape, we must first remember that celestial objects have a beastly nature. Our solar system is located on one arm of the Milky Way, orbiting a central bulb containing 200 to 400 billion stars. The Milky Way itself is a community of more than 60 galaxies known as the Local Group.

Thanks to the work of an international team led by Brent Tully from the University of Hawaii in the United States and consisting of French astronomer Helen Cortois, we have known since 2014 that the local group is only a small component. And thousands of other galaxy clusters of the superstructure of Lanieca (Hawaii’s “paradise”).

Large migration of galaxies

This superstructure draws a network of filaments connected to the intersection shelter regions of the superclusters of the galaxy. These filaments of galaxies and dark matter – five times their abundance – move in the same direction at speeds of 400 to 600 kilometers per second, a kind of gravitational waterway known as the Great Attractor. By migrating to denser areas, galaxies leave wider and empty areas.

In 2019, Brent Tully’s team mapped a vast cosmic desert (150 to 230 million light-years) along the Milky Way border, known as the local void. Our galaxy is part of the “skin” that separates the vast vacuum bubble known as the local sun. The boundaries of our galaxy rotate rapidly toward the centaur and square stars on one side of the dense galactic current, and galaxies rarely change on the other.