The smoothed distribution of galaxies in and around the Vela supercluster. Picture: THOMAS JARRETT/UCT
The smoothed distribution of galaxies in and around the Vela supercluster. Picture: THOMAS JARRETT/UCT

A new concentration of galaxies has been discovered by an international team of astronomers, the University of Cape Town announced on Wednesday.

The previously unknown galaxies uncovered in the Vela constellation were until now hidden from sight by the Milky Way.

This new concentration of galaxies has been dubbed the Vela Supercluster and is about 800-million light-years from earth.

A supercluster of galaxies is the largest and most massive known structure in the universe. It can stretch 200-million light-years across the sky.

The team of astronomers that discovered the supercluster are from SA, the Netherlands, Germany, and Australia, and were led by Prof Renée Kraan-Korteweg from the University of Cape Town.

Kraan-Korteweg said most the famous supercluster ever discovered was the Shapley Supercluster in the 1930s. This is about 650-million light-years away from earth.

Kraan-Korteweg said the Vela is probably of equal mass to Shapley, which posed questions as to how such large structures could exist so close to each other.

"Shapley is already very big and for some time people thought: ‘Can we actually have such large structures in the universe?’ and now we found another that is not very distant from [Shapley] and it looks like it is as massive," Kraan-Korteweg said.

She said it took as long as it did to discover the Vela because of its position as it was obscured by dust, stars and background galaxies.

Both Vela and Shapley are in the same region in the sky and both are pulling their local group of galaxies including the Milky Way towards their centre.

Kraan-Korteweg said it was always hypothesised that Milky Way was being attracted to "the point in the sky", but it was unclear where that extra pull was coming from. She said now they might have found something that explains it.

"To have such objects in relative proximity is quite amazing so they will be pulling us in the same direction," said Kraan-Korteweg.

The discovery was based on multi-object spectroscopic observations which look at the interaction between matter and electromagnetic radiation. The astronomers looked at spectroscopic observations of thousands of partly obscured galaxies.

In 2012, the refurbished spectrograph of the Southern African Large Telescope confirmed that eight new clusters reside within the Vela area. Subsequent spectroscopic observations through the Anglo-Australian Telescope in Australia revealed the vast extent of this new structure.

Dr Michelle Cluver, from the University of the Western Cape, analysed the spectra almost as soon as the photons hit the spectrograph. She said: "As I looked at each new spectrum, it became obvious we were uncovering a massive network of galaxies, extending much further than we had ever expected."

Kraan-Korteweg said Australia’s Square Kilometre Array Pathfinder and SA’s MeerKAT can pave the way towards mapping the central core of the supercluster.

She cited a proposal to use the radio telescope in early-science mode when 32 of its total of 64 dishes are in place during 2017 for a systematic search of the fully hidden core of the super cluster.

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