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17 April 2014 12:48 pm ,
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Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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The Purest Star
30 October 2002 (All day)
Astronomers have found a primitive star that preserves a chemical record of the infant cosmos. The little star, just now facing the end of its long life, dates to an era immediately after the formation of the very first stars.
Ever since stars began to shine, they have been relentless element factories. Stars transform the raw products of the big bang--mostly hydrogen and helium--into heavier elements such as carbon, oxygen, silicon, and iron. When stars explode as supernovas, they forge massive elements and spray the rich mixtures into space. When astronomers come across a star that doesn't incorporate many of these heavy elements, they know it must predate most supernovas. The oldest star found in the outskirts of the Milky Way, for example, contained about one ten-thousandth as much iron as the sun.
Now, an ambitious survey of more remote parts of the galaxy has uncovered a star 20 times as anemic. Astronomer Norbert Christlieb of the University of Hamburg, Germany, and his colleagues scrutinized the star, called HE0107-5240, in December 2001 with the European Southern Observatory's Very Large Telescope array in Paranal, Chile. Analysis of its light shows that the atmosphere is a strikingly unspoiled broth of hydrogen and helium with the barest dash of heavy elements: just one iron atom for every 7 billion atoms of hydrogen. The star's near-purity suggests that just a few earlier supernovas--and perhaps only one--polluted its primordial composition. "This may be the first example of a true second-generation star," says co-author Timothy Beers, an astronomer at Michigan State University in East Lansing. "It's our best look at the starting recipe that led to the rest of the periodic table [of the elements]."
The team's results, which appear in the 31 October issue of Nature, impress other astronomers. "It's astounding that we can glimpse such an early stage of the universe through the composition of this star," says Catherine Pilachowski of Indiana University in Bloomington. Tiny stars such as HE0107-5240 might have formed as companions to the first short-lived stars, which probably were gigantic and unstable, Pilachowski notes.