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Faint Strings of Galaxies in Empty Space

A team of astronomers based at The University of Western Australia’s node of the International Centre for Radio Astronomy Research has found short strings of faint galaxies in what were previously thought to be empty parts of space.

The universe is full of vast collections of galaxies arranged in clusters connected by long strings. This structure is often called the “cosmic web”.

“The spaces in the cosmic web are thought to be staggeringly empty,” said Dr Mehmet Alpaslan, who led the research. “They might contain just one or two galaxies, as opposed to the hundreds that are found in big clusters.”

Using data from the Galaxy and Mass Assembly (GAMA) survey, Alpaslan and his colleagues found that the small number of galaxies inside these voids are arranged differently. “We found small strings composed of just a few galaxies penetrating into the voids – a completely new type of structure that we’ve called ‘tendrils’,” Alpaslan said.

To discover tendrils, the GAMA team created the largest-ever galaxy census of the southern skies using observations from the Anglo-Australian Telescope. “We weren’t sure what we’d find when we looked at voids in detail, but it was amazing to find so many of these tendrils lurking in regions that have previously been classified as empty,” said co-worker Dr Aaron Robotham.

“This means that voids might be much smaller than we previously thought, and that galaxies that were previously thought to be in a void might just be part of a tendril,” Alpaslan said.

The research has been published in the Monthly Notices of the Royal Astronomical Society.