It’s a big universe out there.

Now astronomers are getting a better idea of just how big, thanks to a new 3-D map of the local universe, the most complete ever created.

Covering a distance of 380 million light-years (the Milky Way galaxy is about 100,000 light-years in diameter), the map, unveiled this month at the Harvard-Smithsonian Center for Astrophysics, took more than 10 years to create and finally assembles in one image the location and distance of more than 43,000 galaxies.

“It’s exactly like making a map of the whole Earth and flattening it out,” said Dr. Karen Masters, an astronomer at Britain’s University of Portsmouth and one of the researchers who helped create the image. “It’s nice to finally have a map of the universe . . . it’s where we live.”

Masters told the Star that the map will help astronomers as they tackle the mystery of why the Milky Way — the galaxy to which the Earth and its solar system belongs — moves in relation to its surroundings. Scientists have figured out that the Milky Way is moving through space at about 600 kilometres per second due to gravitational forces, but the source of this gravity has yet to be pinpointed.

“The gravity of all the structures around us is pulling on us and has caused our system to move. This map now shows the local structures, and from this information, we hope to find the things that have the strongest gravity,” she said.

Work on the map began in the late 1990s by the late John Huchra, an astronomer at the Harvard-Smithsonian Center for Astrophysics, who assembled images made by the Two-Micron All-Sky Survey.

The survey used two telescopes — one at the Fred Lawrence Whipple Observatory on Mt. Hopkins in Arizona and one at the Cerro Tololo Inter-American Observatory in Chile — to scan the entire night sky using near-infrared wavelengths of light, which penetrate opaque clouds of dust better than visible light.

The near-infrared scans also allowed astronomers to map in detail areas previously hidden due to their proximity to the plane of the Milky Way galaxy — the dark line running through the middle of the map — an area heavily obscured by stars and dust.

Huchra then combined these scans with “redshift” measurements, which indicate how far away galaxies are from Earth.

As the universe expands, it “redshifts” light coming from galaxies into longer wavelengths. By measuring these longer wavelengths or redshifts coming from a galaxy, astronomers can deduce the distance of the object from Earth. In other words, the higher the redshift, the farther away a galaxy is. It is these measurements that give the map its vital third dimension.

Each dot on the map indicates a single galaxy made up of billions of stars. Red galaxies are the farthest away, while purple galaxies are closest.

Huchra died in October before completing the study, leaving his fellow astronomers, like Masters, to put the finishing touches on the map.

Mike Hudson, a physics and astronomy professor at the University of Waterloo, says the map will aid him in his research into dark matter, a mysterious and unmeasurable substance that scientists believe makes up most of the universe.

“Dark matter doesn’t shine and doesn’t absorb or scatter light, and we can’t even see it directly, but we know it’s there because we can see its gravitational effects,” Hudson told the Star. “The distribution of galaxies on this map we think is a tracer of what the underlying dark matter is doing.”

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Hudson, who likens dark matter to an undetected sub-atomic particle, said the map shows the universe is not expanding in a uniformly smooth fashion — a symptom, he believes, of the gravitational effects of dark matter.

“We can try to measure this uneven expansion and from this,” he says, “we can learn about dark matter directly.”