News 2010

‘High-resolution’ numerical simulations carried out by scientists at the Astrophysics Department of the CEA-Irfu/AIM  have just revealed that the most famous galactic collision ever, the Antennae collision, produces far more stars than observations suggested. When two galaxies meet, the resulting gas compression causes the ignition of new stars. Until now, it seemed that these new stars appeared only in high-density regions, mainly near the core of the collision. A computer re-creation of the collision, with a sufficiently high resolution to pick out the smallest gas clouds for the first time, shows that the starburst is in fact distributed far more uniformly inside the large number of star superclusters scattered across the disks of the galaxies. This important result helps scientists to understand why, in certain collisions, around 100 to 1000 stars per year can appear at the same time. This work was published in Astrophysical Journal Letters.

An international team of astronomers, including several French researchers, has just completed a precise measurement of the distance to five distant galaxies using the ESA Herschel Space Observatory together with ground-based data from the interferometer operated by the Institute for Millimetric Radioastronomy (IRAM)¹ . The research team has shown that the light from these galaxies has travelled for around ten thousand million years before reaching Earth. In order to obtain these results, the team developed an entirely new technique, making use of the 'gravitational lens' effect for the first time in the sub-millimetric domain² . Such a gravitational lens provides a form of magnifying glass on a cosmic scale that can be detected by Herschel. Until now very difficult to observe, these distant and rapidly evolving galaxies are a key component in improving our understanding of the history of the galaxies in our Universe. These results were published in the journal Science on November 5, 2010.

Numerical simulations peformed by a group of astrophysicists of the  AIM-CEA Saclay Laboratory  (University Paris Diderot, CEA, CNRS) and the Nice observatory, based on images collected by the Cassini mission, show that some tiny moons of Saturn are still forming now from material of the Saturn's rings, some billion years after the  end of the formation of planets and satellites inside the Solar system. The simulations can also give some clues about the formation of the Earth's moon. These results are published in the June 10th issue of the Nature magazine. 

The central black hole of the Galaxy, today surprisingly quiet, has undergone, several hundred years ago, a violent phase of activity. This is the conclusion reached by an international team led by astrophysicists of the APC laboratory and including scientists of the Service d'Astrophysique of CEA-Irfu, by studying the high energy emission of molecular clouds located in the central regions of the Galaxy. The scientists have indeed discovered complex variations of this emission, with some of them showing propagation velocity greater than the speed of light. They reveal that a giant outburst, most probably generated by the black hole, took place about 400 years ago. The powerful flare is visible today after reflection by the molecular clouds that play the role of celestial mirrors. The recent history of the region retraced in this way shows that the black hole of the galactic centre is not so different from the supermassive black holes of the active galactic nuclei. This work, based on two long term observing programs of the XMM-Newton and Integral satellites, is the object of two complementary publications in  The Astrophysical Journal.

Following its launch on 14 May 2009, the Planck satellite [1] has been continually observing the celestial vault and has mapped the entire sky since 13 August to obtain the first very high resolution image of the dawn of the universe. The Planck satellite has just finished its first sky coverage. The preliminary images reveal undreamed of details of emissions of gas and dust in our own galaxy. Scientists from CEA-IRFU, as part of a broad international collaboration, are currently working on the extraction and exploitation of the catalogues of objects detected by Planck. These preliminary catalogues are essential to understanding and subtracting stray foreground emissions from the background light of the universe, a fossil trace of its earliest epochs. It is also improving understanding of the formation of the largest structures in the universe, clusters of galaxies. The first catalogue will be published in January 2011. In contrast, the definitive scientific publications on the first light of the universe are not expected until the end of 2012.

Magnetars form a class of neutron stars with a much higher (100-1000 times) magnetic field with respect to common rotation powered pulsars. This extreme magnetic field is currently believed to be the cause of their unpredictable and intense activity. But the observation by an international team, which includes a researcher from AIM/Service d’Astrophysique of CEA-Irfu, of the magnetar dubbed SGR 0418+5729 casts some doubts about this classification. By observing the rotation period of this object for more than one year, scientists have derived that the intensity of the surface magnetic field of this magnetar was much more fainter than that of other objects of this class, and similar to the one of ordinary pulsars. The magnetar-like activity could then be a phase in the life of some pulsars, and magnetars could be potentially much more numerous within our Galaxy. This study has been published in Science Express Magazine on the 14th of October 2010.