* Astronomy

When the very first stars lit up, they may have been fuelled by the dark matter that has long eluded scientists.
These "dark stars," first born nearly 13 billion years ago, might still exist today. Although they would not shed any visible light, astronomers might detect these invisible giants - some 400 to 200,000 times wider than our sun and 500 to 1,000 times more massive - because they should spew gamma rays, neutrinos and antimatter and be linked with clouds of cold, molecular hydrogen gas that normally would not harbour such energetic particles.
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Simulations Illuminate Universe's First Twin Stars
The earliest stars in the universe formed not only as individuals, but sometimes also as twins, according to a paper published today in Science Express. By creating robust simulations of the early universe, astrophysicists Matthew Turk and Tom Abel of the Kavli Institute for Particle Astrophysics and Cosmology, located at the Department of Energy's SLAC National Accelerator Laboratory, and Brian O'Shea of Michigan State University have gained the most detailed understanding to date of the formation of the first stars.

"We used to think that these stars formed by themselves, but now we see from our computer simulations that sometimes they have siblings. These stars provide the seeds of next generation star formation, so by understanding them we can better understand how other stars and galaxies formed" - Matthew Turk.

To make this discovery, the researchers created an extremely detailed computer simulation of early star formation. Into this virtual universe they sprinkled primordial gas and dark matter as it existed soon after the Big Bang, data they obtained from observations of the cosmic microwave background. This mostly uniform radiation - a faint glow of radio waves spread across the entire sky - contains subtle variations that reflect the beginning of all structure in the universe.

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Dans un quasar très éloigné, énorme formation détoiles aux limites des lois physiques

Comment les premières étoiles ont été formées ? Des indications concrètes ont été trouvées pour la première fois par une équipe internationale  de chercheurs, dont un directeur de recherche du CNRS. En observant l'une des galaxies les plus éloignées connue à ce jour (un quasar formé moins d'un milliard d'années après le Big Bang) ils ont réussi à dénicher un nombre gigantesque d'étoiles en son coeur, un chiffre si énorme qu'il approche les limites des lois physiques. Cette découverte est d'autant plus intéressante qu'elle réfute une théorie longtemps nourrie selon laquelle les premières étoiles se seraient formées de manière dispersée dans tout le volume des jeunes galaxies. La détection a pu être réalisée grâce à l'interféromètre du Plateau de Bure de l'IRAM (Institut de Radioastronomie Millimétrique : CNRS-INSU, MPG, IGN) dans les Hautes-Alpes.

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When the universe was still young, they were already dying.
The first stars ever to grace the cosmos with light were brutish monsters, so the story believed by most astronomers goes, lumbering clouds of hydrogen and helium hundreds of times more massive than the Sun. They lived fast and bright and died hard, exploding or collapsing into massive black holes less than a billion years after the Big Bang, never to be seen again.
But they might have left something behind, a buzz of radio waves emitted by high-energy particles spit from the doomed gas swirling around those black holes.
Has that buzz, a cry from the vanished ancestors of our Sun, now been heard?

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