The map they created based on the images shows clumps of dark matter, which also happen to be where scientists believe galaxies were most likely to have formed. The long-term goal of the team, which includes more than 300 scientists from around the world, is to understand why the universe is expanding at an ever-faster rate.
They’re reconstructing eight billion years’ worth of the history of the universe (which is thought to be nearly 14 billion years old) through these snapshots. “That will give us a first, real indication of what dark energy is about,” Frieman says. The team will keep taking pictures for the next three years, and the resulting images will let them test their theories on how the universe has evolved to this point—and where we’re going, literally, as the Milky Way hurtles ever farther through the universe.
The $40 million camera built at Fermilab is mounted on a massive telescope in Chile, in part because it isn’t very windy there. “Stars twinkle because of turbulence,” says Frieman. “If you take a picture through turbulence, the star would be fuzzed out.”
Because these galaxies are so far away, the snapshots require long exposures. For each spot in the sky, the camera takes 10 pictures over five years, each time leaving the shutter open for 90 seconds. Researchers analyze the composite image to see where the light wiggles—a sign that dark matter is present and bending the light with its gravitational pull.
This map, based on measurements created from the composite photos, accounts for about two million galaxies. The dark red represents regions packed with galaxies and, therefore, a lot of dark matter. “It’s analogous to a terrain map,” Frieman says. “Blue is like valleys, where there’s less stuff.”
For more photos, visit darkenergysurvey.org.