News 2012

Nov 05, 2012
Computation of the X-ray emission of a supernova remnant

An international team of astrophysicists, including Samar Safi-Harb and Gilles Ferrand at the University of Manitoba (Canada) and Anne Decourchelle from the Astrophysical Department-AIM Laboratory (CEA Saclay - France), has produced the first 3D simulations of supernova remnants (SNRs) showing the effect of particle acceleration at the wave fronts generated by these powerful X-ray sources in our galaxy. The research is published in the last issue of the Astrophysical Journal.
 

Oct 09, 2012
New type of cosmic ray discovered after 100 years

Using the European X-ray astronomy satellite XMM-Newton [1], researchers from CNRS [2] and CEA [3] have discovered a new source of cosmic rays. In the vicinity of the remarkable Arches cluster, near the center of the Milky Way, these particles are accelerated in the shock wave generated by tens of thousands of young stars moving at a speed of around 700,000
km/h. These cosmic rays produce a characteristic X-ray emission by interacting with the atoms in the surrounding gas. Their origin differs from that of the cosmic rays discovered exactly a hundred years ago by Victor Hess, which originate in the explosions of supernovae. The findings are published in the October issue of the  Astronomy & Astrophysics journal.
 

Jul 05, 2012
Discovery of a transient radio jet from an intermediate-mass black hole

Sporadic ejections of matter are observed in the form of radio jets from supermassive black holes in active galaxies as well as from galactic binary systems hosting a black hole of several solar masses. Do these observations indicate that jet formation is a universal property of black holes, regardless of their mass? The detection, for the first time, a transient radio jet from an intermediate-mass black hole by an international collaboration led by two French teams (IRAP in Toulouse and Service d'Astrophysique-Laboratoire AIM from CEA-Irfu at Saclay) finally settles the debate. The observations of the source HLX-1, using the ATCA radio telescope in Australia, have also helped to constrain the black hole mass to be between 9000 and 90,000 solar masses. This result, published in Science Express on 2012 July 5, provides a bridge between the two extremes of the population of black holes.

Feb 03, 2012
First experimental approach of the asymmetric explosion of a star

The explosive death of massive stars begins with the collapse of their iron core which gives birth to a neutron star. Despite spherical initial conditions, this explosion can kick the neutron star several hundred kilometers per second. Exclusively studied by numerical simulations so far, the hydrodynamic instability responsible for this asymmetry is revealed here in a simple experiment. Making use of the analogy between surface waves in water and shocks in a compressible gas, it describes the mechanism contributing to the neutron star kick and spin at birth. The work led by Thierry Foglizzo at the Astrophysical Department - AIM laboratory (CEA/Irfu - CNRS - University Paris Diderot) and co-workers is an original combination of theory, numerical simulations and experimental analogy addressing a complex astrophysical phenomenon. These results are published in Physical Review Letters, February 3, 2012.
 

Nov 28, 2012
The planetary rings may be at the origin of most of the satellites around planets

Two scientists from the Université Nice Sophia Antipolis - Observatoire de la Côte d’Azur and from the Université Paris Diderot and CEA, have just proposed the first model to explain the origin of most of the regular satellites in our solar system. First proposed in 2010 to explain the repartition of the moons around the planet Saturn, this model is now extended to reproduce the distribution of the numerous satellites around the other giant gazeous planets (Jupiter, Neptune,…) and could as well explain the formation of satellites around the "rocky planets (Earth, Pluton,…). For all these planets, their moons may have formed from rings of matter that do not exist anymore today. These results are crucial to understand the universal laws that lead to the apparition of moons around planets. They are published in the last issue of the Science magazine (30 Novembre 2012).

Jul 06, 2012
The formation of a brown dwarf

A team led by Philippe André du Service d'Astrophysique-Laboratoire AIM du CEA-Irfu has just uncovered the very first stage of the formation  of a brown dwarf, one of these tiny stars with a mass just above the planets. Several hundreds brown dwarfs have already been detected in the galaxy but up to now it was impossible to observe their formation. Thanks to the great interferometer of IRAM (Institute de Radioastronomie Millimétrique), the scientists have located a compact condensation of gas and dust with a temperature of only 10 degrees above the absolute zero and a mass approximatively 2% the solar mass. These characteristics are exactly what expected to give birth to a brown dwarf. The discovery of this first proto brown dwarf is published in the Science magazine of July 6th, 2012

 

For a more detailed account, see the French version.

 

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