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17 June 2015

The incredible map that reveals our place in the universe - and it's about to get a lot bigger

  • Earlier this year, scientists revealed the Milky Way's position in an enormous supercluster of galaxies
  • Huge supercluster stretches 500 million light years across and has the mass of a hundred quadrillion suns 
  • Milky Way is on fringes of cosmic web, which has been named Laniakea - meaning 'immeasurable heaven
  • The team is now mapping out an even greater concentration of galaxies, known as the Shapley Supercluster

Dr Brent Tully made headlines earlier this year when he unveiled a road map of the universe with pathways between the Milky Way and 100,000 other far away galaxies.

Now the University of Hawaii professor is hoping to map out an even greater concentration of galaxies, known as the Shapley Supercluster, to help us better understand our place in the universe. 

It's a massive task. The Shapley Concentration is so huge that it is pulling our home supercluster, including us, toward the constellation Centaurus in the southern sky.

'I don't think the story is going to be close to well understood until our maps are encompassing the whole domain around the Shapley Concentration,' Tully told Discover magazine.

The project would involve maps stretching to over a billion light-years.

'It's a huge job, but doable on a time-scale of decades,' said the University of Hawaii professor.

The Shapley Supercluster was discovered in the 1930s by American astronomer Harlow Shapley, as a remarkable concentration of galaxies in the Centaurus constellation.

Boasting more than 8,000 galaxies and with a total mass more than ten million billion times the mass of the sun, it is the most massive structure within a distance of about a billion light-years from our Milky Way Galaxy. 

The hot gas pervading galaxy clusters shines brightly in X-rays, but it is also visible at microwave wavelengths, which Planck sees as a distinctive signature in the Cosmic Microwave Background – the afterglow of the Big Seed. 

The new work follows the identification by Dr Tully of the full extent of Earth’s home supercluster of 100 thousand galaxies. The team named this Laniakea - Hawaiian for 'immeasurable heaven'.

The astonishing discovery revealed that the Milky Way - home to Earth and our solar system - is on the fringes of the enormous cosmic web.

Dr Tully led the team of scientists that mapped Laniakea's boundaries from measurements of the velocities of local galaxies.

The researchers compared the galactic movement with that of water in a landscape of hills and valleys, tracing the outer surface of a region where the net-motion of galaxies was inward.

They wrote in the journal Nature: 'We define a supercluster to be the volume within such a surface, and so we are defining the extent of our home supercluster, which we call Laniakea.' 

The vast road map may look as though it is densely packed, however there are vast expanses of darkness where nothing can be found for hundreds of light years. 

Our supercluster is the first to be mapped and shows galaxies strung out along glowing pathways that are held together by gravity as the groups make their way through space. 

Scientists have long-known that galaxies are not distributed randomly but congregate together in clusters. When these clusters meet in the cosmos, they create giant superclusters, like Laniakea. 

To put the sheer size of the supercluster into context, the Earth is the third planet from our sun, which is one of just billions of stars within the Milky Way. Other than being our home, our galaxy is nothing special and is one of around 100,000 within our supercluster.

And even though the collection of bright galaxies is incomprehensibly large, it makes up just a corner of the observable universe. 

Within Laniakea, galaxies flow inwards towards a region called the Great Attractor, the equivalent of a large gravitational valley.

Around our supercluster are four others - they include Shapley, along with Hercules, Coma and Perseus-Pisces - however it is difficult to show exactly where our neighbourhood of galaxies ends and the others begin.