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3-D Universe
June 07, 2000
Band of galaxies
Still from the movie, showing a band of galaxies. The blackness on either side of the band is actually filled with even more galaxies that the 2dF Survey did not observe.
image: AAO

Until now, astronomers could only observe our universe in two dimensions. But a group of astronomers have announced completion of the largest-ever three-dimensional survey of galaxies, creating a 3-D map that covers 13 billion billion billion cubic light years worth of space (that’s 13 followed by 27 zeros).

Then they turned the whole thing into a movie.

A picture is worth millions of worlds

At a meeting of the American Astronomical Society, Karl Glazebrook, assistant professor of physics and astronomy at Johns Hopkins University announced that the survey also reveals a critical result for astronomers—that the universe is to expand forever.

As it turns out, the density of the universe is not great enough to slow its expansion. In fact the expansion, which began at the "Big Bang," is accelerating slightly and will continue to do so. The unprecedented size of the survey makes the calculations extremely reliable.

Large-scale structure
There is an incredible amount of structure on different scales in our Universe: planets, stars, galaxies and the "large scale structure" seen here. Each dot in this image represents a galaxy in the 2dF Galaxy Redshift Survey, while the blue structures help to highlight regions where the density of galaxies is high.
image: AAO

By measuring the distance to 400 galaxies at a time, the scientists were able to calculate the density of matter in the universe. As their remarkable new movie shows, the universe is "lumpy"—consisting of massive clusters of galaxies, but with huge voids in between.

"We’re not really in the center of the universe," notes Glazebrook. "We’re actually in a very empty part of the universe, nowhere special at all....The map makes it look like we’re in the center but if we fill all the axes in three dimension, everywhere you see we’re just nowhere important at all."

However, Glazebrook does make one comforting observation. "We’re sort of in a moderately well-to-do area of the universe...there are much richer areas much full of galaxies, but also much poorer areas devoid of galaxies. We’re sort of in the middling to average suburb."

The 2dF

Glazebrook is a member of the 2dF Galaxy Redshift Survey Project. This team of 30 scientists and 11 institutions uses arguably the most complicated astronomical instrument ever built to perform its groundbreaking work. In its three years of operation, 2dF has detected and measured more than 100 million galaxies—only one-third of its goal.

The 2dF, or 2-degree field instrument, uses a robotic arm to point 400 optical fibers at a time at known positions of galaxies. A computer automatically measures the distances, resulting in the first accurate 3-D map of a huge section of the heavens. This groundbreaking new instrument is housed at the Anglo-Australian Observatory (AAO) in New South Wales, Australia.

The 2dF
The 2dF
image: AAO

The instrument gives AAO’s largest telescope a two-degree field of view, or four times the width of the full moon. The instrument measures each galaxy’s position and distance from Earth with a spectrograph, which splits the light emitted by each cosmic object into its component wavelengths, or spectrum.

"That tells us how fast the galaxy is moving from us because the universe is expanding from the Big Bang," Glazebrook explains.

The 2dF measures the distances between the Earth and galaxies outside our Milky Way Galaxy by means of the galaxies’ Doppler. As objects recede away from us, the wavelength of visible light, or spectrum, they exhibit shifts to longer wavelengths, such as the red (and are therefore called red shifts). The farther into the red an object shifts, the more distant it is from Earth. Glazebrook’s team uses this information to calculate the immense distances of galaxies from our own galaxy, providing the third dimension lacking from previous maps.

The scientists have already performed 3-D measurements of over 100 million galaxies, and expect that 250 million galaxies will be measured at the survey’s conclusion.

Universe: The Movie

"Visualizations are very important in understanding our structure of the universe" says Glazebrook. "People think visually. Statistics is not enough."

The newest images to come from the 2dF project are in an incredible computer simulation. The movie uses actual positions of galaxies and clusters captured by the 2dF instrument to ‘fly’ through the wonders of our universe.

It begins at the lens of the AAO telescope. The camera swoops up through the telescope’s view and into space, banks ‘right,’ and flips about like a starfighter in a science-fiction movie.

All the while, galaxies, star clusters and nebulae so clear and bright that they dazzle the human eye swirl into our view, and out again. Ahead are ever more wonders—gas clouds in every color of the rainbow, brilliant stars and galaxies—all showcased against the remorseless black of the cosmos.

At last, the camera brings us home, and one final glimpse into the sky shows the viewer how little an area of space 2dF has mapped. This last view shows us how much more work lies ahead for the hard-working astronomers, and their expertly-crafted instruments that extend the gaze of humanity ever farther into the limitless universe.

Artists of Space

Some astronomer-photographers have become artists in photographing the wondrous sights of our universe. One of the best photographers is David Malin of AAO. His and other space artists’ photographs can be found at the AAO Picture Gallery.

Other sites where you can view the best in space photography:

Hubble Space Telescope Pictures

Solar and Helospheric Observatory—great screensaver available!

Chandra X-Ray Observatory Center

EarthKam—Students’ Space Photo Web Site

Elsewhere on the web:

Sloan Digital Sky Survey

"Voyage Through the Universe"

The Royal Greenwich Observatory

National Radio Astronomy Observatory

by Debra Utacia Krol

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