Astrophysicists published the largest 3D map of the universe ever made, filling in 11 billion years of history

• Astrophysicists have released the largest three-dimensional map of the universe ever made.
• The map helps fill in 11 billion years of the universe's history.

Astrophysicists have created the largest-ever three-dimensional map of the universe — it encompasses more than 2 million galaxies and supermassive black holes.

The effort, which involved more than 100 astrophysicists from around 30 institutions worldwide, was built on 20 years of scientific observations.

The map, shown below, puts Earth at the center. Points farther from that center represent galaxies farther away, which also means they existed further back in the past, since the universe has been expanding since the Big Bang. Each color-coded section of the map refers to the type of galaxy astrophysicists detected and mapped in that section: closer galaxies are shown in blue, and quasars are in yellow.

The map helps to fill in a major gap in astrophysicists' knowledge of the universe's history — an 11 billion year gap.

Scientists know what the universe looked like soon after it began, thanks to decades of research about the Big Bang. They also have a good sense of what the universe has looked like for the past few billion years. But given that the universe is about 13.8 billion years old, a lot of time wasn't accounted for.

"It was as if we had this movie of the universe but with most of it missing," Julian Bautista, a research fellow at the University of Portsmouth's Institute of Cosmology and Gravitation, said in a press release. The new map, the researchers say, provides valuable information about what happened during those 11 billion years.

A key finding revealed in the map (and backed up by other recent research) is that the universe began to expand more quickly about 6 billion years ago. Its expansion has accelerated ever since.

Researchers believe this acceleration is due to dark energy — a mysterious, unknown force that makes up about 68% of the universe — but they don't know for sure.

"We can finally see most of the universe's tale and how dark energy was one of the main actors in it," Bautista said.

To fill in the latest 6 billion years of the map, researchers mapped large galaxies with low star-forming activity, which give off red light and are shown in the image at the top of this story as sprinklings of red and pink dots. Further out in time, they mapped galaxies with hotter, younger stars, which give off blue light and are shown as blue dots in that image. To fully close the 11-billion-year gap, they mapped quasars: massive and bright galaxies with supermassive black holes at their centers, which appear in yellow.

In conjunction with the three-dimensional map, the researchers released more than 20 scientific papers describing their findings.

In a statement, Will Percival, a research scientist at the extended Baryon Oscillation Spectroscopic Survey, called the final product "the most accurate expansion history measurements over the widest-ever range of cosmic time."

The new map also revealed a discrepancy between the universe's previously accepted rate of expansion, called the Hubble constant, and the rate calculated based on how far Earth is from the closest nearby galaxies. One possible explanation for this, Bautista told Business Insider, is that a different type of dark energy was present in the very early universe, altering the rate of expansion.