Nothing quite puts existence into perspective like a map of the universe, and this is the grandest map of them all.
An international team of astronomers from the Sloan Digital Sky Survey III have assembled the largest ever three-dimensional map of the distant cosmos that includes a survey of 1.2 million galaxies. It's a monumental project that aims to get a better grip on the mysterious force called dark energy that permeates the universe, reports New Scientist.
“Over the last decade we have prepared and conducted the largest survey of the universe yet,” said Rita Tojeiro, 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.”
Every single dot on this map represents an entire galaxy, and the map is so large that the depiction shown above is only a sliver of the whole map. And as extensive as the full map is, the 1.2 million galaxies surveyed still only represent a small portion of the total number of galaxies believed to exist in the entirety of the universe. That number is likely somewhere around one hundred billion.
Using the map, scientists were able to measure dark energy thanks to a system called BOSS, or Baryon Oscillation Spectroscopic Survey. Basically, the system uses how galaxies are distributed in the universe to estimate the size of so-called "baryonic acoustic oscillations," pressure waves that formed in the early universe. The expansion rate of the universe can then be more carefully studied in this way.
Dark energy is the theoretical repulsive force that counteracts gravity. It's what many astronomers believe explains why our universe is expanding at an accelerating rate instead of pulling itself together.
Interestingly, the map shows that large clusters of matter tend to form due to their gravitational attraction, as predicted by general relativity. This indicates that our theories about gravity are sound despite the fact that the universe continues to expand, which further supports the idea that a mysterious force must be at play: dark energy.
What this dark energy is remains a puzzle, but perhaps this map will be the key to unlocking some of those secrets.