Posted: Thu Dec 20, 2007 6:14 am Post subject: Our Solar System
Solar system was born 4568 mn yrs ago
Washington, Dec 20: A new research has dated the earliest step in the formation of the solar system – when microscopic interstellar dust combined into mountain-sized chunks of rock – to 4,568 million years.
The research was carried out by Frederic Moynier, postdoctoral researcher, Qing-zhu Yin, assistant professor of geology, and graduate student Benjamin Jacobsen from the UC (University of California) Davis.
“The physics and timing of this first stage of planet formation are not well understood. So, putting time constraints on the process should help guide the physical models that could be used to explain it,” said Yin.
The researchers established the dates by analyzing a particular type of meteorite, called a carbonaceous chondrite, which represents the oldest material left over from the formation of the solar system.
Carbonaceous chondrites are made up of globules of silica and grains of metals embedded in black, organic-rich matrix of interstellar dust. The matrix is relatively rich in the element manganese, and the globules are rich in chromium.
Looking at a number of different meteorites collected on Earth, the researchers found a straight-line relationship between the ratio of the amount of manganese to that of chromium, the amount of matrix in the meteorites, and the amount of chromium-53.
“These meteorites never became large enough to heat up from radioactive decay, so they have never been melted,” said Yin. “They are cosmic sediments," he added.
“By measuring the amount of chromium-53, they could work out how much of the radioactive isotope manganese-53 had initially been present, giving an indication of age,” said Yin. “They then compared the amount of manganese-53 to slightly younger igneous (molten) meteorites of known age, called angrites,” he added.
The UC Davis researchers estimate the timing of the formation of the carbonaceous chondrites at 4,568 million years ago, ranging from 910,000 years before that date to 1,170,000 years later.
"We've captured a moment in history when this material got packed together," said Yin.
Indian has new theory on Big Bang
London, April 17: A new controversial analysis by an astronomer of Indian origin has suggested that the Big Bang might not have come at the beginning of the Universe, but after a long and slow period of shrinkage.
According to a report, the theory has been put forward by Amit Yadav, an astronomer at the University of Illinois at Urbana-Champaign.
If this theory holds any ground, it would show that the early universe did not inflate with the smoothness that many theorists expected. "The standard, canonical models will be ruled out if this holds," said Yadav. "The simplicity is gone," he added.
Yadav`s result suggests that models of inflation - a furious hyperexpansion in the instant after the Big Bang, 13.7 billion years ago - have to be much more complicated than previously thought, or else that inflation never occurred at all and that the Big Bang came after a period of contraction.
"If the result sticks, it would be the first time that one of the predictions of simple inflation failed. And it could also lead to a radical reinterpretation of what the Big Bang was and whether it marked the universe`s beginning,"he said.
Standard, simple inflation – needed to achieve a flat, smooth universe - holds that, just after the Big Bang, a uniform negative gravitational field drove a brief period of accelerated expansion.
Then the field died out, creating the matter and energy known in the universe today and leaving an afterglow of microwave radiation just a few degrees above absolute zero. If simple inflation theory is right, this imprint should be almost, but not quite, perfectly gaussian - a pattern with smooth-looking noise.
The analysis of Yadav and adviser Benjamin Wandelt showed that the CMB map was not gaussian with a certainty of 99.5%
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