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The mysterious 'Great Attractor' pulling the Milky Way galaxy off course

This illustration shows the Milky Way, our home galaxy.
This illustration shows the Milky Way, our home galaxy.

No matter what you're doing right now – sitting, standing, walking – you're moving.

Specifically, you're moving at least four different ways.

First, Earth is spinning around on its axis at about 1,000 miles per hour right now, or about 1,600 kilometers per hour. This rotation is the reason we have days. Second, Earth and other planets in our solar system are orbiting the sun. Our planet does that at around 67,000 miles per hour, or about 108,000 kilometers per hour. That's why we have years. And third, you're moving because the sun and the rest of our solar system is orbiting the center of the Milky Way galaxy at over 500,000 miles per hour, or 828,000 kilometers per hour.

On top of all that, you're moving because the entire universe is expanding outward. All the time.

But in the 1970s, astrophysicists noticed that something was off about our galactic neighborhood, or Local Group. The whole clump of neighboring galaxies were being pulled off course at over one million miles per hour, towards something we couldn't see.

They called this region the Great Attractor. But their ability to study it was limited.

"The Milky Way has millions and millions of stars and a lot of dust, which is blocking all that information that we could be measuring in that direction. So our own galaxy's blocking the Great Attractor," says Jorge Moreno, a computational astrophysicist at Pomona College. This area we cannot see is known to researchers as the Zone of Avoidance.

Scientists still don't know the full details of what and exactly how the Milky Way and its neighboring galaxies off course, but there have been several candidates over the last few decades.

Most recently, the prime suspect is the supercluster Laniakea, which is Hawaiian for 'immense heaven' or 'immeasurable heaven.'

Curious about other cosmic mysteries? Email us at shortwave@npr.org.

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Today's episode was produced by Rachel Carlson. It was edited by Rebecca Ramirez. Rebecca, Rachel and Regina checked the facts. Maggie Luthar was the audio engineer.

Copyright 2024 NPR

Regina G. Barber
Regina G. Barber is Short Wave's Scientist in Residence. She contributes original reporting on STEM and guest hosts the show.
Rachel Carlson
Rebecca Ramirez (she/her) is the founding producer of NPR's daily science podcast, Short Wave. It's a meditation in how to be a Swiss Army Knife, in that it involves a little of everything — background research, finding and booking sources, interviewing guests, writing, cutting the tape, editing, scoring ... you get the idea.