Deformed Galaxies Confirm Universe's Acceleration
By SPACE.com Staff
posted: 26 March 2010
12:01 pm ET
An exhaustive study of nearly half a million deformed galaxies observed by the Hubble Space Telescope has revealed definitive proof of the acceleration of our universe's expansion.
A team of astronomers took a close look at more than 446,000 galaxies observed by Hubble in 557 overlapping photographs — making it the largest survey ever performed by the iconic space telescope. The observations, taken from Hubble's COSMOS study, are the latest confirmation of what scientists have long thought, that a mysterious force called dark energy is driving the universe to not just expand, but to expand at an ever-faster pace.
"The sheer number of galaxies included in this type of analysis is unprecedented, but more important is the wealth of information we could obtain about the invisible structures in the universe from this exceptional dataset," study co-author Patrick Simon from Edinburgh University said in a statement.
Astronomers have long known that the universe is expanding based on observations dating back to 1929, when famed astronomer Edwin Hubble — namesake of the Hubble Space Telescope — measured the cosmic speeds of many galaxies. He discovered that those galaxies were all moving away as they sped across the universe.
In 1998, two teams of astronomers announced that not only was the universe expanding, but it was accelerating as well. In fact, the farther away a galaxy is from Earth, the faster it is moving away, researchers have said.
Ultimately, theory holds, galaxies will recede so far from each other that light from one galaxy won't reach the others, and intergalactic observations and communications will become impossible. Only local groups of galaxies are expected to hang together, and even that's uncertain over the long term. One wild idea has the runaway expansion leading to a Big Rip, when perhaps 30 billion years from now even the stars of an individual galaxy fly apart and finally planets are ripped asunder. Then, even atoms won't be able to hold together.
The universe's acceleration also confirms Albert Einstein's theory of general relativity, since the expansion was required by the famed scientist's cosmological constant in that famed equation.
In the new study, astronomers used the so-called "weak gravitational lensing" effect of distorted distant galaxies to measure the distribution of matter across the universe on a cosmic scale. They also measured the distances to 194,000 of the galaxies observed by Hubble using ground-based telescopes.
The research will be detailed in an upcoming issue of the Astronomy and Astrophysics.
The new observations give astronomers a clue into how matter in the universe clumps together due to gravity, and then is driven apart by dark energy.
"Dark energy affects our measurements for two reasons. First, when it is present, galaxy clusters grow more slowly, and secondly, it changes the way the universe expands, leading to more distant — and more efficiently lensed — galaxies," said study co-author Benjamin Joachimi from the University of Bonn. "Our analysis is sensitive to both effects."
There's an added bonus to the study, too. It also helps build a clearer map of the universe and how galaxies are strewn about it, researcher said [more galaxy photos].
"Before, most of the studies were done in 2D, like taking a chest X-ray. Our study is more like a 3D reconstruction of the skeleton from a CT scan," explained study co-author William High of Harvard University. "On top of that, we are able to watch the skeleton of dark matter mature from the Universe's youth to the present."
Click to view image: 'pc1'
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