07-17-2010, 05:22 PM
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Karyu
Dreaming Of Pandora
Nostalgia++
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Join Date: May 2010
Location: Ireland
Posts: 1,381
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Dark Matter Mystery May Have Been Solved.
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Cosmologists invented Dark Matter in an effort to balance the equation of how much mass there should be in the universe. For years these scientists were baffled by the fact that their calculations and observations showed that the universe is missing a whopping 50% of the mass it should have, the other half being normal matter. To try and make sense of the mystery they replaced this 'missing matter' with 'Dark Matter'. However, recent observations show that the universe's missing matter is not missing at all and that Dark Matter is merely a myth.
Quote:
One of the great, unsolved mysteries of 21st-century science is the existence of the missing matter of the universe. Using observations with NASA's Chandra X-ray Observatory and ESA's XMM-Newton, astronomers detected a vast reservoir of intergalactic gas about 400 million light years from Earth. This discovery is the strongest evidence yet that the "missing matter" in the nearby Universe is located in an enormous web of hot, diffuse gas.
This missing matter — which is different from dark matter -- is composed of baryons, the particles, such as protons and electrons, that are found on the Earth, in stars, gas, galaxies, and so on. A variety of measurements of distant gas clouds and galaxies have provided a good estimate of the amount of this "normal matter" present when the universe was only a few billion years old. However, an inventory of the much older, nearby universe has turned up only about half as much normal matter, an embarrassingly large shortfall.
The mystery then is where does this missing matter reside in the nearby Universe? This latest work supports predictions that it is mostly found in a web of hot, diffuse gas known as the Warm-Hot Intergalactic Medium (WHIM).
Scientists think the WHIM is material left over after the formation of galaxies, which was later enriched by elements blown out of galaxies.
"Evidence for the WHIM is really difficult to find because this stuff is so diffuse and easy to see right through," said Taotao Fang of the University of California at Irvine and lead author of the latest study. "This differs from many areas of astronomy where we struggle to see through obscuring material."
[...]
Confirmed detections of the WHIM have been made difficult because of its extremely low density. Using observations and simulations, scientists calculate the WHIM has a density equivalent to only 6 protons per cubic meter. For comparison, the interstellar medium -- the very diffuse gas in between stars in our galaxy -- typically has about a million hydrogen atoms per cubic meter.
"Evidence for the WHIM has even been much harder to find than evidence for dark matter, which is invisible and can only be detected indirectly," said Fang.
There have been important detections of possible WHIM in the nearby Universe with relatively low temperatures of about 100,000 degrees using ultraviolet observations and relatively high temperature WHIM of about 10 million degrees using observations of X-ray emission in galaxy clusters. However, these are expected to account for only a relatively small fraction of the WHIM. The X-ray absorption studies reported here probe temperatures of about a million degrees where most of the WHIM is predicted to be found.
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