SpaceJibe

May 21, 2011

Galactic Census Confirms Existence of Mysterious ‘Dark Energy’

Filed under: Big Bang, Cool, Cosmology, Gamma Ray Bursts — bferrari @ 7:45 am
New results from NASA's Galaxy Evolution Explorer and the Anglo-Australian Telescope atop Siding Spring Mountain in Australia confirm that dark energy (represented by purple grid) is a smooth, uniform force that now dominates over the effects of gravity (green grid). The observations follow from careful measurements of the separations between pairs of galaxies

New results from NASA's Galaxy Evolution Explorer and the Anglo-Australian Telescope atop Siding Spring Mountain in Australia confirm that dark energy (represented by purple grid) is a smooth, uniform force that now dominates over the effects of gravity (green grid). The observations follow from careful measurements of the separations between pairs of galaxies (examples of such pairs are illustrated here). (NASA/JPL Caltech)

A census of 200,000 galaxies may confirm that the mysterious force of dark energy is what is pulling the universe apart at ever-increasing speeds, a new study finds.

The results of the five-year galactic survey offer new support for the favored theory of how elusive dark energy works — as a constant force, uniformly affecting the universe and driving its runaway expansion.

The new findings contradict an alternate theory that gravity, and not dark energy, is the force pushing space apart and causing it to expand. That alternate theory challenges Albert Einstein’s concept of gravity, because it has gravity acting at great distances as a repulsive force rather than an attractive one. [6 Weird Facts About Gravity]

The survey, which looked at galaxies that were up to 7 billion years old, used data from NASA’s space-based Galaxy Evolution Explorer (GALEX) and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.

An unsolved mystery

Dark energy has long been an unexplainable force, and the theory of its existence remains unproven, but the results of this new study could provide independent confirmation that it is behind the strange way that galaxies are being pulled from one another, against the tug of gravity. [What Is Dark Energy?]

“The action of dark energy is as if you threw a ball up in the air, and it kept speeding upward into the sky faster and faster,” said Chris Blake of the Swinburne University of Technology in Melbourne, Australia. Blake is lead author of two papers on the study appearing in an upcoming issue of the journal Monthly Notices of the Royal Astronomical Society.

“The results tell us that dark energy is a cosmological constant, as Einstein proposed,” Blake said in a statement. “If gravity were the culprit, then we wouldn’t be seeing these constant effects of dark energy throughout time.” [Top 10 Strangest Things in Space]

Dark energy is thought to dominate the cosmos, making up roughly 74 percent of the universe. Dark matter, a slightly less mysterious substance, accounts for 22 percent. “Normal” matter, which consists of anything with atoms, or the materials that make up living creatures, planets and stars, makes up only about 4 percent of the universe.

Where did it come from?

The theory of dark energy was proposed during the late 1990s, based on studies of distant explosions of dying stars called supernovas. Supernovas emit constant, measurable light, which make them useful guideposts for astronomers to calculate the dying stars’ distance from Earth.

By looking farther into space, scientists are effectively able to peer back in time, since the light we see from distant objects is light that left there billions of years ago. Astronomers observed many supernovas at different distances to determine how fast they are speeding away from us, and these measurements subsequently implied a strange force – dark energy – was flinging the objects out at accelerating speeds.

The new survey provides two separate methods for independently checking these results. This is the first time astronomers performed these checks across the whole cosmic time span dominated by dark energy.

Astronomers began by assembling the largest three-dimensional map of galaxies in the distant universe, as spotted by GALEX.

“The Galaxy Evolution Explorer helped identify bright, young galaxies, which are ideal for this type of study,” said Christopher Martin, principal investigator for the mission at the California Institute of Technology in Pasadena, Calif. “It provided the scaffolding for this enormous 3-D map.”

Mapping the cosmos

Detailed information about the light for each galaxy was obtained from the Anglo-Australian Telescope, and the team of astronomers studied the pattern of distance between them. Sound waves from the very early universe left imprints in the patterns of galaxies, causing galactic pairs to be separated by approximately 500 million light-years.

Blake and his colleagues used this figure as a yardstick to determine the distance from the galaxy pairs to Earth. Similar to the supernova studies, these distance data were combined with information about the speeds the galaxy pairs are moving away from us.

This revealed, yet again, that the fabric of space is stretching apart faster and faster.

The astronomers also used the galaxy map to study how clusters of galaxies grow over time like cities, eventually containing many thousands of galaxies. The gravitational pull of the clusters attracts new galaxies, but dark energy appears to tug them apart, and scientists are able to measure dark energy’s repulsive force.

“Observations by astronomers over the last 15 years have produced one of the most startling discoveries in physical science: The expansion of the universe, triggered by the Big Bang, is speeding up,” said Jon Morse, director of the astrophysics division at NASA headquarters in Washington, D.C. “Using entirely independent methods, data from the Galaxy Evolution Explorer have helped increase our confidence in the existence of dark energy.”

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1 Comment »

  1. Refer to the website address below for the evidence of dark energy: http://news.nationalgeographic.com/news/2008/08/080811-dark-energy.html

    The following is the extract from the above websites under the fourth paragraph:

    The new image reveals the spectral fingerprints created by dark energy as it stretches huge supervoids and superclusters, structures that are roughly half a billion light-years across.

    Dark energy is being defined in http://en.wikipedia.org/wiki/Dark_energy as a hypothical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Despite there was an image to reveal the existence of something, or the so-called, dark energy, that it could stretch huge supervoids and superclusters even up to half a billion light-years across, it might not provide the truth that the universe could be expanding due to the following possibilities:

    a)The universe itself could be created initially in infinity and there might be no space limit or boundary. If that could be our universe to be since nobody in this earth did ever see any boundary of this universe, the thing that stretches huge supervoids and superclusters, structures to move would not lead to the conclusion that this universe could be expanding. Instead, it simply gives information that something has been causing the huge supervoids and superclusters to move forward.

    b)There could be also the possibility that this universe could be so huge that it could take a few trillion light years for galaxies to travel from one end to another in order to have their return facing us in a few trillion light years later.

    There are a few likeliness that would not give the conclusion that the universe could be expanding by seeing that thing that stretches huge supervoids and superclusters across and there are:

    1)The so-called, dark energy, might simply perform its routine function to cause the huge supervoids and superclusters to be stretched across and yet it is either within the huge boundary of the universe in which it would take a trillion years for the galaxies to travel from one end to another until its final return in advancing to us in a few trillion years later or in the universe that could have been created to be lasted until infinity.

    Let’s refer to another website pertaining to the velocities of the galaxies in advancement: http://www.newscientist.com/article/dn7109-evidence-of-dark-energy-missed-30-years-ago.html

    The following is the extract for the analysis:

    In 1972, Allan Sandage of the Carnegie Observatories in Pasadena, California, US, reasoned that in the nearby universe – where the expansion is at its slowest – the gravitational attraction between groups and clusters of galaxies should produce significant deviations in their velocities from the otherwise largely smooth speed of expansion. These deviations are called “peculiar velocities”, but Sandage pointed out that galaxies in our vicinity – those lying just beyond our “Local Group” of the Milky Way and its immediate neighbours – showed abnormally low peculiar velocities.

    Let’s assume that you would blow a balloon. The air would go from one end and to move in one direction to cause the balloon to expand. However, consideration has to be taken in is the moving speed for all particles in the balloon should be the same regardless whether those particles that are nearby each other or big or small to the ultimate reach of the boundary of the balloon so as to cause it to expand further. There should not be any reason for all particles within the balloon to travel with various speeds despite the particles could be big or small.

    As discovered by Allan Sandage of the Carnegie Observatories in Pasadena, California, in 1972 that there is a significant deviations in their velocities among galaxies, it does not provide a good source to prove the galaxies might be expanding. If there could be a constant force that could cause the universe to be expanded, the moving speed for all the galaxies should be the same in advancing further away from us instead of with irregular velocities that some are advancing faster than another.

    The deviation of velocities of galaxies in advancement is mentioned the same in the website as follows: http://www.universetoday.com/16170/astronomers-find-new-evidence-for-dark-energy/

    The following is the extract:

    When the team compared galaxies against the CMB, they found that the microwaves were a bit stronger if they had passed through a supercluster, and a bit weaker if they had passed through a supervoid.

    As the velocities of all the galaxies have been deviated from each other, it is irrational to be quick to jump into the conclusion that our universe could be expanding so as to use it to support Big Bang theory in which something can be created out of nothing.

    Comment by Jason Tannery — August 27, 2011 @ 12:52 am


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