Laniakea: Our home supercluster

Defining regions in an infinite universe is tricky business: Clusters of dozens of galaxies, called local groups, are further bound into clusters containing hundreds of galaxies. The Laniakea supercluster, described in a paper published in this week’s Nature, is 500 million light-years in diameter and contains 100,000 galaxies – and we sit at the very edge of it. Together, those galaxies carry 100 million billion times the mass of our sun.

How can such a massive number of galaxies be connected? While some areas of space are basically empty, others contain highly concentrated star power. In these areas, the supercluster galaxies are drawn toward each other in intricate ways. According to R. Brent Tully, an astronomer at the University of Hawaii at Manoa and lead author of the study, galaxies in the cosmos can be compared to water on Earth.

“Within a land form, water flows in certain directions,” Tully said. “The water knows, even if the land is very flat, which way is downhill.” Instead of downhill valleys that attract water flow, our universe has something called the “Great Attractor.” This region serves as a gravitational focal point , influencing the motion of galaxies in the supercluster.

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