Daniel Eisenstein and SDSS-III
A slice through the map of the large-scale structure of the Universe from the Sloan Digital Sky Survey and its Baryon Oscillation Spectroscopic Survey. Each dot in this picture indicates the position of a galaxy six billion years into the past. The image covers about 1/20th of the sky, a slice of the Universe 6 billion light-years wide, 4.5 billion light-years high, and 500 million light-years thick. Color indicates distance from Earth, ranging from yellow on the near side of the slice to purple on the far side.
Now, an international team of scientists on the hunt for this dark energy have created the largest ever 3D map of the universe, measuring the positions of more than 1 million galaxies 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," Rita Tojeiro, who co-led the team, told the Independent.
The map was created using data from the Baryon Oscillation Spectroscopic Survey (BOSS), which looked at "pressure waves" traveling through the universe.
"These are viewed as if they are sound waves, to produce an "acoustic" imprint," the New Scientist writes. "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."
The scientists saw a dramatic connection between the sound wave imprints seen in this cosmic afterglow 400,000 years after the Big Bang to the clustering of galaxies 7-12 billion years later, Tojeiro said.
When the BOSS program was planned, scientists had already determined that dark energy had a significant influence on the expansion of the universe starting about 5 billion years ago. The goal of BOSS was to measure back even further, to 7 billion years ago.
So far, the scientists have found that if dark energy has been driving the expansion of the universe over that time, it's evolving very slowly (if at all).
"The change is at most 20 percent over the past seven billion years," said Florian Beutler, who led two of the papers that were submitted this week.