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Blobrana


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The case of the lithium that has gone missing since the Big Bang has been solved -- the stars swallowed it, scientists said on Wednesday.

The discrepancy between the quantity of lithium estimated to have been created at the start of the universe and the small amount now actually found has long perplexed astronomers, bringing into question fundamental planetary theory.
Scientific theory said that up to three times the amount of lithium -- the lightest of the solid elements -- was produced along with the main elements hydrogen and helium in the Big Bang than can now be found in the older stars.
But now a team led by Andreas Korn from the Uppsala Astronomical Observatory in Sweden say they may have finally solved the riddle.
Writing in the science journal Nature they said that whereas other elements were hurled back into the atmosphere by convection, lithium was dragged down into the star where it was destroyed when temperatures rose over 2 million degrees.
Based on observations of 18 stars of different ages, the team calculated that the original lithium content was 78 percent higher than that currently found -- enough to account for the discrepancy with Big Bang estimates.

"We thus conclude that diffusion is predominantly responsible for the low apparent stellar lithium abundance in the atmospheres of old stars by transporting the lithium deep into the star".

Source: REUTERS

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Blobrana


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A process similar to a conveyor belt transports heavy elements from the surface of stars into their interiors where they are destroyed, new observations suggest.

The findings, detailed in Thursday's issue of the journal Nature, support the idea that the abundance of heavy elements in stars decreases with time and could help solve the cosmological lithium problem, a riddle that has been puzzling astronomers for years.
Lithium is one of the few elements thought to have been produced during the Big Bang, but when astronomers compare the amounts of lithium contained within the atmospheres of the very old stars in our Milky Way galaxy, they find their predictions are higher by a factor of 2 to 3.
Researchers trying to resolve this problem used the European Southern Observatory's Very Large Telescope in Chile to study a globular cluster containing half a million ancient stars called NGC 6397, located 7,200 light-years from Earth. The stars varied in age and were at different stages in their evolution.
The researchers found that as the stars age, the proportion of lithium in their atmospheres first slightly increases and then drops off sharply. The process is thought to take billions of years.
The researchers extrapolated backwards in time to determine what the stars' original lithium content was, and found that the value was in good agreement with that predicted by Big Bang theory.

"The cosmological lithium discrepancy is thus largely removed" - Andreas Korn, study team member, Uppsala Astronomical Observatory in Sweden.

Scientists think that that stellar rotation and internal gravity waves are among the physical mechanisms contributing to lithium destruction, but more studies are needed to confirm this.

"The ball is now in the camp of theoreticians" - Andreas Korn.

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