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Astrophysicists see dark energy slowing universe

  • 17 December 2008
  • Written by 
  • Published in Space
For the first time, astronomers have seen through the eyes of the NASA Chandra space telescope what is being called “arrested development” of the universe (slowing of the expansion of the universe), which is caused specifically by the effects of dark energy.

The NASA article “Dark energy found stifling growth in the universe” states, “By tracking how dark energy has stifled the growth of galaxy clusters and combining this with previous studies, scientists have obtained the best clues yet about what dark energy is and what the destiny of the universe could be.”

Dark energy is a hypothetical type of energy that supposedly permeates all of space. It exerts a negative pressure (kinda like a negative gravity effect) that seems to account for the differences in how scientists think visible matter in the universe should behave (theory) and how it actually behaves (observation).

Unlike visible matter, dark energy it thought to only act on dark matter, a hypothetical form of matter that does not reflect nor emit electromagnetic radiation (such as visible light, x-rays, and gamma rays).

The NASA astronomers used the Chandra X-ray Observatory to make their conclusions. After years of research, the results, according to NASA, “… provide a crucial independent test of dark energy, long sought by scientists, which depends on how gravity competes with accelerated expansion in the growth of cosmic structures.”

Astrophysicists and other scientists working on how the universe was first formed (and how it operated in the past, why it works now, and what it will look like in the future) consider the understanding of dark energy as “one of the biggest problems in science.”

Alexey Vikhlinin, of Smithsonian Astrophysical Observatory (SAO), Cambridge, Massachusetts, U.S.A., led the research team. Vikhlinin states, “This result could be described as 'arrested development of the universe.’ Whatever is forcing the expansion of the universe to speed up is also forcing its development to slow down."

Page two continues dark energy, Einstein's cosmological constant, the fate of the universe and other such things.

The Chandra space telescope observed hot gas in many different galaxy clusters scattered throughout the universe, some close together, and others far apart.

The Vikhlinin team found that the mass of the galaxy clusters, which are gravitationally-bound bodies (from ten to thousands of galaxies) that come together to form the densest parts of the universe, has increased over time.

Such action of coming together by these celestial objects agrees with a universe partially controlled by dark energy. NASA explains: “It is more difficult for objects like galaxy clusters to grow when space is stretched….”

Another research member of the Vikhlinin team, William Forman (also with the Smithsonian Astrophysical Observatory), stated, "For years, scientists have wanted to start testing how gravity works on large scales and now, we finally have. This is a test that general relativity could have failed."

The information found with Chandra provides scientists with a much better picture of the properties of dark energy.

Vikhlinin adds, "Putting all of this data together gives us the strongest evidence yet that dark energy is the cosmological constant, or in other words, that 'nothing weighs something.’"

He states, "A lot more testing is needed, but so far Einstein's theory is looking as good as ever."

NASA comments on page three.

NASA concludes by stating, “These results have consequences for predicting the ultimate fate of the universe.”

And adds, “If dark energy is explained by the cosmological constant, the expansion of the universe will continue to accelerate, and the Milky Way and its neighbor galaxy, Andromeda, never will merge with the Virgo cluster."

"In that case, about a hundred billion years from now, all other galaxies ultimately would disappear from the Milky Way's view and, eventually, the local superclusters of galaxies also would disintegrate.

Look for two journal articles concerning the dark energy discovery of the Vikhlinin’s team in the February 10, 2009 issue of The Astrophysical Journal.

Want to know more about dark energy?

Please go to the NASA Goddard Space Flight Center "Imagine the Universe" website "Dark Energy."

And, PhysicsWorld.com has a lengthy and informative article on its website "Dark Energy."


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