How we found a supercluster of 100,000 galaxies

Courtois's and her team's evolving map of galaxies (Photo: Hélène Courtois)

A visualization of a galaxy map. (Courtesy of Hélène Courtois)

Astrophysicist Hélène Courtois works to chart the movement and locations of galaxies. “Our galaxy moves at the staggering speed of 630 kilometers per second,” she says in a talk at TEDxLyon, and it is not the only astronomical system hurtling through space. The Milky Way is just one of billions of galaxies (as far as we can estimate) — and the cosmic layout of those galaxies is a cartological mystery that Courtois and her colleagues are still trying to suss out.

To do this, Courtois and her team use data from a set of very powerful radio telescopes to measure the speeds and positions of thousands of galaxies, determining how fast and in which ways they move. These measurements have allowed Courtois and her team to better map and delineate the structure of the universe, figuring out how galaxies are arranged across huge stretches of space.

After three years of research, observing the Universe, day in and day out, and trying to make sense of the maps they made, Courtois’s galaxy-mapping team came across a breakthrough, she says in her talk. They discovered “a watershed line between the galaxies belonging to our physical structure [and] galaxies that move towards another structure,” she says. This line turned out to the boundary line for a supercluster, the supercluster in which we exist, “the largest galaxy structure in the Universe,” Courtois says. This supercluster, which Courtois and her team called Laniakea (“Huge heavenly horizon” in Hawaiian) is part of our new cosmic address.

“That supercluster we live in is immense,” Courtois says. “Take our galaxy, multiply it by 100,000, add a million smaller galaxies and you get Laniakea.”

For more, watch Courtois’s whole talk below:

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