A team of researchers from CEA (Astrophysical Department and CEA-DAM) and the LUTH Laboratory (Paris Observatory) has just published a comprehensive study of an enigmatic phenomenon of quasi-periodic oscillations at the surface of strongly magnetic white dwarfs also called "Polars ". These dense stars are orbiting a companion and capture its material that falls freely toward the white dwarf poles. Strongly heated to millions of degrees, the hot gas or plasma then emits mainly in X-rays. Thanks to detailed numerical simulations of the plasma behavior, the researchers were able to reconstruct the existence of strong instabilities leading to rapid oscillations in the luminosity with timescales of only a few seconds. However, using the database of the XMM-Newton satellite, these oscillations were sought unsuccessfully by the team, in the X-ray emission of over 20 Polars. This contradiction leads today researchers to propose to study the phenomenon in the laboratory. Indeed, similar physical conditions can currently be replicated by large power lasers like the LMJ . The control of plasma instabilities is a key element for nuclear fusion by magnetic (ITER experience) ou inertiel confinement (laser Mégajoule) and instabilities of white dwarfs could contribute to a better understanding of this general phenomenon. These results are the subject of two articles published in the journal Astronomy & Astrophysics, July 2015.
|see the movie of the numerical simulation (short version)|
As part of an observing program carried out with the Hubble Space Telescope, a group of researchers from the “Service d’Astrophysique-Laboratoire AIM” of CEA-IRFU led by Anita Zanella discovered the birth cry of a massive star-forming clump in the disk of a very distant galaxy. This giant clump is less than 10 million years old, and it is the very first time that such a young star-forming region is observed in the distant Universe. This discovery sheds new light on how stars were born within distant galaxies. The physical properties of this object reveal that newly-born clumps in such galaxies survive from stellar winds and supernovae feedback, and can thus live for a few hundred million years unlike the predictions from several theoretical models. Their long lifetime could enable their migration toward the inner regions of the galaxy, hence contributing to the total mass of the galactic bulge and the growth of the central black hole. These results are published in the “Nature” journal from May 2015.
A team from the laboratory "Astrophysics, Instrumentation, Modeling" Paris-Saclay (AIM - CNRS / CEA / Université Paris Diderot) has developed a new model representing the evolution of protoplanetary disks over millions of years. These giant structures made of dust and gas are the privileged place of planet formation due to the presence of what researchers call "traps planets." With this new model, the scientists were able to determine the most favorable places to form the planets. These results are published online in the journal Astronomy & Astrophysics on May 6, 2015.