News 2003

Jul 10, 2003
The cosmic kaleidoscope

As it travels near matter concentrations, visible or dark, light does not travel in a straight line. It is instead deflected by gravity, as if it went through a lens. This effect, known as "gravitational lensing", is predicted by the theory of General Relativity and is currently observed by large telescopes. It distorts the shape of galaxies like a cosmic kaleidoscope and allows scientists to map the distribution of mass in the Universe. This new technique is currently used by several international teams of astronomers who measure this "cosmic shear", the very small distortions produced on the images of distant galaxies by large scale structures (groups and clusters of galaxies) on the line of sight.
An important review of this subject, written by Alexandre Refregier, astrophysicist at the Service d'Astrophysique at CEA-DAPNIA Saclay, will appear this fall in the series "Annual Reviews of Astonomy and Astrophysics". It includes a history of this fast-evolving field, a summary of the most recent measurements, and a presentation of the perspectives offered by future instruments.

Mar 01, 2003
A new source of chemical elements

An international collaboration led by two French astronomers, Martine Mouchet from the Paris-Meudon Observatory and Jean-Marc Bonnet-Bidaud from the Astrophysical Department of the French Atomic Energy Commission (CEA), have just uncovered a very peculiar abundance of carbon, nitrogen and oxygen, the three major elements for life, at the surface of a white dwarf in a tight couple of stars called magnetic cataclysmic variables (MCVs). The origin of this anomaly is still not fully elucidated. It may have been produced by a uncommon "quiet" nova explosion at the surface of the white dwarf but the most likely explanation lies in a peculiar evolution of the companion star. This opens new ways to produce the essential CNO elements in the Galaxy.

 

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