Berkeley Lab helps develop largest 3-D map of galaxies

Daniel Eisenstein and SDSS-III/Courtesy

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A team of more than 100 scientists, including members of the Lawrence Berkeley National Laboratory, have developed the world’s largest, three-dimensional map of distant galaxies.

This map records the presence of 1.2 million galaxies, which, according to Berkeley Lab astrophysicist and principal investigator David Schlegel, will likely help advance the scientific understanding of major astronomical concepts such as dark energy and the expansion of the universe.

In order to create this map, the team of scientists utilized the Sloan Digital Sky Survey telescope at Apache Point Observatory, which produces a map of the sky. Through this telescope, and through the use of a light-splitting device called a spectrograph, the scientists were able to disperse the light from the distant galaxies and record it, converting two-dimensional images of the sky into three-dimensional images.

The spectrograph is fundamentally different from taking a picture,” Schlegel said. “It produces a colored picture of not just a few colors, like your eye can see, but 4,000 different colors.”

Schlegel added that the different colors show how much galaxies have redshifted — representing a movement of galaxies away from Earth through the expansion of the universe.

Scientists have been observing the sky with the Sloan Digital Sky Survey telescope for 18 years, but not until recently were they able to pinpoint galaxies outside of the 1 million brightest galaxies. With this new three-dimensional map, scientists now have a map that covers approximately 40 percent of the universe.

From this map, scientists have already observed a recent expansion of dark energy in the universe. Schlegel described dark energy as the fifth force of the universe, the other four being gravitational force, electromagnetic force, strong nuclear force and weak nuclear force. The existence of dark energy was unknown to astronomers until 1998.

“The universe is expanding, but what dark energy is doing is that it’s pushing that expansion faster and faster,” Schlegel said. “So the universe is not just expanding — it’s also accelerating.”

Shirley Ho, an astrophysicist at Berkeley Lab, said in an email that the results of the three-dimensional map will now require scientists to study the universe through even bigger telescopes, as well as through radio telescopes and gravity waves telescopes, to discover even more about the presence of dark energy in the universe.

According to Schlegel, scientific knowledge of dark energy is currently limited to the understanding that it is not a particle. Schlegel hopes that this new three-dimensional map will lead scientists to develop a more concrete definition of dark energy and a more comprehensive awareness of the cause of its existence.

“We’re looking for clues,” Schlegel said. “We want to gain a better understanding of not only the history of the universe, but also the future of the universe.”

Contact Harini Shyamsundar at [email protected] and follow her on Twitter at @hshyamsundar.