Space

Map of nothing: Astronomers size up the vast void next door to the Milky Way

Map of nothing: Astronomers si...
This simulated image shows a cube slice of the "cosmic web" structure that permeates the cosmos, with blue and white representing galaxies and the darker sections representing voids with very little matter
This simulated image shows a cube slice of the "cosmic web" structure that permeates the cosmos, with blue and white representing galaxies and the darker sections representing voids with very little matter
View 2 Images
This simulated image shows a cube slice of the "cosmic web" structure that permeates the cosmos, with blue and white representing galaxies and the darker sections representing voids with very little matter
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This simulated image shows a cube slice of the "cosmic web" structure that permeates the cosmos, with blue and white representing galaxies and the darker sections representing voids with very little matter
A 3D image of the Local Void's shape. The Milky Way lies at the center point of the XYZ arms
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A 3D image of the Local Void's shape. The Milky Way lies at the center point of the XYZ arms

Our home galaxy is right on the border of a void so vast it's hard to picture. To get a better idea of its shape and size, a team of astronomers has mapped out the edges of this extragalactic emptiness, and calculated just how much gravitational influence it has on the Milky Way.

Just like the Earth orbits the Sun and the Sun orbits the center of the Milky Way, our home galaxy is itself racing through the cosmos at tremendous speeds. In fact, it seems to be moving much faster than it should be, were it only under the influence of the expansion of the universe. The Milky Way, along with nearby neighbors like Andromeda and a host of smaller galaxies, has been clocked at about 2 million km/h (1.3 million mph).

This discrepancy could be explained by the distribution of mass on gigantic scales. Galaxies aren't evenly spread out across the cosmos – they tend to clump together into clusters, connected by thin strands of material like a spider web. That leaves large sections of space relatively empty – and as astronomers discovered in 1987, the Milky Way is right on the fringe of one of them.

This Local Void, as it's known, has been estimated to be between 146 and almost a billion light-years wide, which is unfathomably empty. And it seems to be getting bigger. A few years ago astronomers found that a particularly low-density area dubbed the Dipole Repeller is pushing away the Milky Way and other galaxies in the Local Sheet – an almost flat cluster of galaxies that makes up one wall of the void.

But the Local Void is hard to study, mostly because it's a region of nothing hiding behind the huge concentration of stars and matter at the center of the Milky Way galaxy. For the new study, the team measured the movements of 18,000 galaxies detailed in a dataset called Cosmicflows-3. Using that, the researchers constructed a 3D cosmographic map and found that the walls of the Local Void came into sharp focus.

A 3D image of the Local Void's shape. The Milky Way lies at the center point of the XYZ arms
A 3D image of the Local Void's shape. The Milky Way lies at the center point of the XYZ arms

The team also used this information to calculate how much influence the Local Void is exerting on our galaxy. After accounting for the speeds expected as the universe expands, the researchers found that about half of the motion of our galactic cluster is created "locally," as the massive Virgo cluster pulls us towards it and the Local Void pushes us away.

It's also been argued that empty regions like the Local Void and the Dipole Repeller aren't actively pushing matter away. Instead, areas of high density naturally attract more matter towards them, making the voids larger and therefore give the appearance that they're repelling matter.

The new research was published in the Astrophysical Journal. The team details the shape and structure of the Local Void with 3D models in the video below.

Source: University of Hawaii

Cosmicflows-3: Cosmography of the Local Void

5 comments
Edward Vix
So impressive that someone was able to determine and present this information, like the cosmos itself, it is so astonishingly complex! All due to chance some would say, but I don't think that's a rational conclusion.
Colt12
And after this someone opens the locker door. Been watching too much Men in Black
Global
Is it as if we are just atoms in an almost infinite thing...
lon4
Seeing the almost random distribution of matter and void spaces represented here, makes me think that the inception of space-time was not exactly a Big-Bang, but more of a Big Splash. The result is very fluid appearing rather than radiating from a center as in an explosion. As though the potential energy of the proto-universe collided with an opposing force.
Don Duncan
"...due to chance some would say..."?? "...an almost infinite thing..."?? "...the almost random distribution of matter..."?? Do you know what you mean by these terms? Could you define them? I think not. They are nonsense, contradictory. For example, how can a "thing" be almost infinite? It's either infinite or not. Or, "almost" random? You either know how the distribution works or it's random to you. What would be the opposite of "some" chance? No chance? "Some" would say pop corn is chance, especially if they have not seen it before. "Chance" depends on the individual's context, it's a measure of knowledge of the event, not the event. These are all epistemological words, words that describe a mental state relative to the event, not the event.