Gigantic Voids are Expanding and Shrinking

The Local Void: 150 million light years across (Credit: NASA)

The Local Void: 150 million light years across (Credit: NASA)

Very few researchers are studying our Universe’s largest structures, but here’s a nice analysis of Voids,  some of the largest structures “we’ve” found so far.

Voids are nearly spherical regions of our universe with few galaxies. They can be described as galaxies on the surface of soap bubbles. One void appears some 3.5 billion (that’s with a “B”) light years across. The largest one confirmed is called the Giant Void at 1.3 Billion light years across.

If you are like me (and most cosmologists), you might have assumed Voids were relatively stable.

Well, apparently not . . .

 Along comes some clever research and analysis using calculations, which found voids are moving and changing size. Small voids are shrinking and large voids expanding; in a seemingly coherent semi-rapid fashion.

A team lead by  Diego G. Lambas of Argentina’s National University of Cordoba examined some 245 voids using Sloan Digital Sky Survey data.

Void in Bootes (Sometimes called "Great Void" this is not the same as the Giant Void in the constellation Canes Venatic.) Credit: Richard Powell, An Atlas of the Universe

Void in Bootes (Sometimes called “Great Void” this is not the same as the Giant Void in the constellation Canes Venatic.) Credit: Richard Powell, An Atlas of the Universe

While it is not currently possible to examine the sideways motion of  a Void or a galaxy, they did look at the apparent recession velocities of the Voids and found some new dynamics. They found that some Voids move at 300–400 kilometres per second faster than their surroundings indicate.

Not just moving, Changing Size

It appears the smaller Voids are shrinking and the larger Voids are expanding.

The researchers hypothesize that gravity in denser parts of the cosmic web of the neighboring walls and filaments is pulling the smaller voids together. In contrast, larger voids tend to occur in less dense areas where gravity from surrounding filaments is pulling them apart.

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References: “The sparkling Universe: the coherent motions of cosmic voids,” by Diego G. Lambas, Marcelo Lares, Laura Ceccarelli, Andrés N. Ruiz, Dante J. Paz, Victoria E. Maldonado, Heliana E. Luparello

Vast cosmic voids merge like soap bubbles, by Ron Cowen, Nature, Oct 2015

 

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