* Astronomy

Dark Matter in Newborn Universe Doused Earliest Stars
Perhaps the first stars in the newborn universe did not shine, but instead were invisible "dark stars" 400 to 200,000 times wider than the sun and powered by the annihilation of mysterious dark matter, a University of Utah study concludes.
The study - to be published next month in the journal Physical Review Letters - calculated how the birth of the first stars almost 13 billion years ago might have been influenced by the presence of dark matter - the unseen, yet-unidentified stuff that scientists believe makes up most matter in the universe.
It is conceivable that gigantic dark stars may exist today, and although they do not emit visible light, they could be detected because they should spew gamma rays, neutrinos and antimatter and be associated with clouds of cold, molecular hydrogen gas that normally wouldn't harbour such energetic particles.

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A groundbreaking study has provided new insight into the way the first stars were formed at the start of the Universe, some 13 billion years ago.

Cosmologists from Durham University, publishing their results in the prestigious international academic journal, Science, suggest that the formation of the first stars depends crucially on the nature of the dark matter, the strange material that makes up most of the mass in the universe.
The discovery takes scientists a step further to determining the nature of dark matter, which remains a mystery since it was first discovered more than 70 years ago. It also suggests that some of the very first stars that ever formed can still be found in the Milky Way galaxy today.

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Title: Population III stars: hidden or disappeared ?
Authors: L. Tornatore, A. Ferrara, R. Schneider

A PopIII/Pop II transition from massive to normal stars is predicted to occur when the metallicity of the star forming gas crosses the critical range Z_cr = 10^(-5 ± 1) Z_sun. To investigate the cosmic implications of such process we use numerical simulations which follow the evolution, metal enrichment and energy deposition of both Pop III and Pop II stars. We find that: (i) due to inefficient heavy element transport by outflows and slow "genetic" transmission during hierarchical growth, large fluctuations around the average metallicity arise; as a result Pop III star formation continues down to z=2.5, but at a low peak rate of 10^-5 M_sun yr^-1 Mpc^-3 occurring at z~6 (about 10^-4 of the PopII one); (ii) Pop III star formation proceeds in a "inside-out" mode in which formation sites are progressively confined at the periphery of collapsed structures, where the low gas density and correspondingly long free-fall timescales result in a very inefficient astration. These conclusions strongly encourage deep searches for pristine star formation sites at moderate (2<z<5) redshifts where metal free stars are likely to be hidden.

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A star, with the not-so catchy name of HE 1523-0901, that's estimated to be 13.2 billion years old (plus or minus 2 billion years) almost as old as our 13.7-billion-year-old Universe. Despite being so old, it's quite nearby; it's in our Galaxy of the Milky Way.

Did we know that stars can be that old?
Yes other really old stars have been found, such as the ancient CS 31082-001, estimated to be 14 billion years old, plus or minus 3 billion years.

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