|
CNES/CNRS Joint Press
Release
Direct measurement of the
magnetic field at the surface of a neutron star was made possible for
the first time with EPIC, the European Photon Imaging Camera, aboard the
European Space Agency's XMM-Newton spacecraft. This value is equal to
approximately eighty billion times the average magnetic field of our sun.
These results were obtained by a Franco-Italian team of the Centre d’Etude
Spatiale des Rayonnements (CESR: a joint research unit of the CNRS, Université
Paul Sabatier of Toulouse, Observatoire Midi-Pyrénées, France),
of the Consiglio Nazionale delle Ricerche of Milan and the Università
degli Studi of Pavia, Italy, and published in the journal, Nature(1)
, on June 12, 2003.
A neutron star is one of the "monsters
of the sky". It is the result of the explosion of a massive star,
a supernova, in which part of the star is ejected into space with the
rest undergoing gravitational collapse and forming a neutron star that
rotates very rapidly. It is actually a celestial body that is so compressed
that it contains a mass on the order of that of our sun within a radius
of 10 km. Matter in the center of a neutron star is in a hyper-condensed
state and cannot be reproduced on the earth. It is a true laboratory of
the extreme limits of physics, thanks to which we have the opportunity
to understand some of the final stages of the evolution of the stars that
fill our universe.
As a result of the temperature of their surface, on the order of several
million degrees, neutron stars are directly observable in X-ray emission
which explains the interest in observing them with the XMM-Newton spaceship
that detects this high-energy radiation. It is one of the cornerstones
of the ESA scientific program, launched into orbit by Ariane 5 in December
1999. The main instrument on board, the EPIC (European Photon Imaging
Camera), was also designed within the framework of a joint European project
with the considerable participation of the CNES, the Centre d’Etude
Spatiale des Rayonnements (CNRS) and the French Atomic Energy Commission,
with Giovanni F. Bignami, head of the CESR at this time, acting as the
project's research director. In August 2002, the telescope was aimed at
an isolated neutron star, 1E1207.4-5209, for two complete orbits, the
longest observation ever made by XMM of an object in our galaxy. This
object, relatively unknown until now, was chosen by the Franco-Italian
team because previous observations had shown three wide absorption lines
that could not be explained.
The results of the analysis of these lines, a joint effort between Toulouse
and Milan, revealed some surprises. The X-rays emitted by the star clearly
showed signs of an extremely big magnetic field that had never been directly
observed on an isolated neutron star although it had been predicted from
a theoretical point of view. Calculations indicated a value of the force
of this magnetic field of approximately 8x1010 gauss. (the overall magnetic
field of the sun is approximately 1 gauss). Presented at a workshop that
was held at Columbia University in New York several weeks ago, these results
were received with enthusiasm by the American scientific community that
had itself tried to obtain these same measurements, but to no avail.
With this first measurement of the magnetic field of an isolated neutron
star, astronomers have come closer to understanding the extreme limits
of physics. With the help of these types of measurements, they will be
able to improve their knowledge of neutron stars and their surfaces, in
particular.
1 - Bignami G.F., Caraveo P.A., De Luca
A., Mereghetti S. The magnetic field of an isolated neutron star from
X-ray cyclotron absorption lines. Nature (2003).
Researcher
contacts:
Giovanni Bignami
CESR. Tel: +33 5 01 55 85 86
E-mail: Giovanni.Bignami@cesr.fr
INSU CNRS contact:
Philippe Chauvin
Tel: +33 1 44 96 43 36
E-mail: philippe.chauvin@cnrs-dir.fr
Press Contact
CNRS:
Martine Hasler
Tel: +33 1 44 96 46 35
E-mail: martine.hasler@cnrs-dir.fr
CNES press contact:
Eliane Moreaux
Tel: +33 5 61 27 33 44
E-mail: eliane.moreaux@cnes.fr
|