Daniel Eisenstein and SDSS-III

Take a look around. The largest ever 3D map of the universe pinpoints the position of more than a million galaxies, and has allowed scientists to make one of the most precise measurements yet of dark energy – the mysterious unexplained force that is causing the universe to expand at an accelerating rate.

“Over the last decade we have prepared and conducted the largest survey of the universe yet,” says Rita Tojeiro at the University of St Andrews in Scotland, who co-led the international team. “By measuring the positions of 1.2 million galaxies over one quarter of the sky, we mapped the three-dimensional structure of the universe over a volume of 650 cubic billion light years. Using this map we were able to make some of the crispest measurements yet of how dark energy is driving the expansion of the universe.”

Hundreds of scientists from the Sloan Digital Sky Survey III project collaborated to make the map.


A system called Boss (Baryon Oscillation Spectroscopic Survey) was used to measure the expansion rate of the cosmos by looking at density pressure waves travelling through the universe.

These are viewed as if they are sound waves, to produce an “acoustic” imprint. By studying the cosmic microwave background – the afterglow of the big bang that gave birth to the universe – the scientists were able to see how the pressure waves had helped to shape the cosmos over time.

“We see a dramatic connection between the sound wave imprints seen in the cosmic microwave background 400,000 years after the big bang to the clustering of galaxies 7 to 12 billion years later,” Tojeiro says.

The map also reveals the distinctive signature of the movement of galaxies towards regions of the universe containing more matter, due to the attractive force of gravity.

A series of papers on the new map have been submitted to the Monthly Notices of the Royal Astronomical Society.