New 3-D map of massive galaxies and distant black holes offers clues to dark matter and dark energy

With such a map, scientists can retrace the history of the universe over the past 7 billion years to get better estimates for how much of the universe is made up of these two mysterious entities.

By New York University — Published: August 8, 2012

Astronomers have constructed the largest-ever three-dimensional map of massive galaxies and distant black holes, which will help the investigation of the mysterious “dark matter” and “dark energy” that make up 96 percent of the universe.

Photo by M. A. Aragón (Johns Hopkins University)/M. SubbaRao (Adler Planetarium)/A. Szalay (Johns Hopkins University)/Y. Yao (Lawrence Berkeley National Laboratory, NERSC)/The SDSS-III Collaboration

Astronomers have constructed the largest-ever three-dimensional map of massive galaxies and distant black holes, which will help the investigation of the mysterious dark matter and dark energy that make up 96 percent of the universe.

The map was produced by the Sloan Digital Sky Survey III (SDSS-III).

Early last year, the SDSS-III released the largest-ever image of the sky, which covered one-third of the night sky. The new data, “Data Release 9” (DR9), which publicly releases the data from the first two years of this six-year project, begins expansion of this earlier image into a full three-dimensional map.

“What really makes me proud of this survey is our commitment to creating a legacy for the future,” said Michael Blanton, a New York University physics professor who led the team that prepared DR9. “Our goal is to create a map of the universe that will be used long after we are done, by future generations of astronomers, physicists, and the general public.”

DR9 is the latest in a series of data releases stretching back to 2001. This release includes new data from the ongoing SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), which will eventually measure the positions of 1.5 million massive galaxies over the past 7 billion years of cosmic time, as well as 160,000 quasars — giant black holes actively feeding on stars and gas — from as long ago as 12 billion years in the past.

BOSS is targeting these big, bright galaxies because they live in the same places as other galaxies and they’re easy to spot, even far away in the universe. Mapping these big galaxies thus provides an effective way to make a map of the rest of the galaxies in the universe.

This video is a fly-through of the SDSS-III galaxies mapped in Data Release 9. Each galaxy in the animation is placed at the location mapped by SDSS and is represented by the zoomed-in template image that matches the actual shape of the galaxy.

Galaxies are concentrated into clusters and filaments with voids in between. The SDSS-III is exploring this structure to determine the nature of dark energy and the distribution of dark matter in the Universe.

Credit: Miguel A. Aragón (Johns Hopkins University)/Mark SubbaRao (Adler Planetarium)/Alex Szalay (Johns Hopkins University)/Yushu Yao (Lawrence Berkeley National Laboratory, NERSC)/SDSS-III Collaboration

With such a map, scientists can retrace the history of the universe over the past 7 billion years. With that history, they can get better estimates for how much of the universe is made up of dark matter — matter that we can’t directly see because it doesn’t emit or absorb light — and dark energy, the even more mysterious force that drives the accelerating expansion of the universe.

“Dark matter and dark energy are two of the greatest mysteries of our time,” said David Schlegel of Lawrence Berkeley National Laboratory, who led the SDSS-III effort to map these galaxies and quasars. “We hope that our new map of the universe can help someone solve the mystery.”

That map of the universe is the centerpiece of DR9. The release includes images of 200 million galaxies and spectra of 1.35 million galaxies, including new spectra of 540,000 galaxies from when the universe was half its present age. Spectra show how much light a galaxy gives off at different wavelengths. Because this light is shifted to longer, redder wavelengths as the universe expands, spectra allow scientists to figure out how much the universe has expanded since the light left each galaxy. The galaxy images, plus these measurements of expansion, are combined by SDSS-III scientists to create the three-dimensional map released with DR9.

Distant “quasars” provide another way to measure the distribution of matter in the universe. Quasars are the brightest objects in the distant universe and their spectra show intricate patterns imprinted by the large-scale clumping of intergalactic gas and underlying dark matter that lies between each quasar and the Earth.

These new data are not only helping us understand the distant universe, but also our own cosmic backyard, the Milky Way galaxy. DR9 includes better estimates for the temperatures and chemical compositions of more than half a million stars in our own galaxy.

“With these better estimates, we can look back at the history of our galaxy,” said Connie Rockosi of the University of California, Santa Cruz, who leads the SDSS-III’s Milky Way study. “We can tell the story of how smaller galaxies came together to build up the Milky Way we see today.”

All these new images and spectra contain the promise of new discoveries about our universe — but the SDSS-III is only in the middle of its six-year survey.

“The most fun part of making this data available online is knowing that anyone on the Internet can now access the very same data and search tools that professional astronomers use to make exciting discoveries about our universe,” said Ani Thakar of Johns Hopkins University.

And DR9 doubtless contains many surprises.

“This is science at its collaborative best,” said Michael Wood-Vasey, a professor at the University of Pittsburgh and the scientific spokesperson for the SDSS-III collaboration. “SDSS-III scientists work together to address big questions extending from our own galaxy to distant reaches of the universe and then they share all of that data with the world to allow anyone to make the next big discovery.”

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FRED KAULLEN from ARKANSAS said:

Well done Stephen. Your explanation helps many of us amateurs that mainly dabble in direct observational astronomy, and struggle with the big picture in cosmology.

I also highly agree with Jim!

Submitted: 8/17/2012 4:28:36 PM (CST)

DAN JACOBS from WASHINGTON said:

Things like this make me love science!

Submitted: 8/17/2012 2:27:32 PM (CST)

NEIL ORMAN from FLORIDA said:

This does not meet my main concern. There is a paradox in our “observable” universe. If the speed of light is finite, at around 300,000 km/sec, how is it that I can stand on my planet and “see” all the way back to the big bang? Or nearly so far back. If the light takes around 13 billion years to reach me, how come I am here first, watching it arrive? Did I travel all that way so fast as to be standing here before the actual light photons reached me? No one has ever explained this paradox to me in simple words. If anyone reading this can give me an understandable response, I would be extremely grateful. Since I have never seen this paradox described before, let alone resolved, I take the liberty to name it after myself: Orman’s Paradox. I will hope for a response.

Submitted: 8/17/2012 1:24:31 PM (CST)

STEPHEN ARMSTRONG from CALIFORNIA said:

Well, Gerardo, the dark matter is distributed where you can see galaxies, and the dark energy is distributed in the gigantic, bubble-shaped voids of empty space between the galaxies. For the first 9 billion years, the expanding voids actually helped gravity condense the dark matter into the galactic structures we see in the video fly-through. This even slowed the expansion of the universe down, not unlike what even Einstein expected! But then, the porosity of the universe increased (like an expanding sponge) past a certain tipping point, and now the universe is more air bubble than "sponge", and nothing can now impede the expanding voids, driven by dark energy. AND, since a huge void causes a huge imbalance in the average gravity field of the galactic region involved, galaxies actually race AWAY FROM a void. This happens because the voids have no matter at all, so galaxies get attracted away from the voids (towards other matter sources) on vectors away from the center of the void. This is happening to The Local Group currently. We are being pulled toward the Virgo Cluster, but "pushed" from behind more strongly and at a large angle by a huge void. This interaction results in a combined vector of motion which is larger than the matter-matter gravitational interaction alone. In other words, dark energy is tearing the universe apart.

Good point, Kenneth! But that's the underestimated and underutilized power of computer simulations: they don't suffer from physical laws! So you can go warp 1 billion or 3 MPH, and the PC won't care. It won't even take the Doppler effect into account, unless you program it to care.

I think Jim speaks best for us all!

Submitted: 8/15/2012 9:31:32 PM (CST)

GERARDO W FISCHER from ARGENTINA said:

This traveling through a space full of galaxies told me nothing as for the understanding of the distribution of dark matter and dark energy.

Submitted: 8/11/2012 10:23:17 AM (CST)

KENNETH A TIPPER said:

Wow... simulated travel incredibly faster than in Star Trek. But wouldn't approaching galaxies that fast blue-shift the light into hard X-rays (at least), rending them invisible and frying the unfortunate traveller? :(

Submitted: 8/9/2012 9:26:29 AM (CST)