Launch anniversary press conference: "Today XMM-Newton is challenging 15-year old concepts"
5 December 2000Providing new insights into black holes and unravelling the composition of intergalactic matter XMM-Newton is certainly living up to its promises. The European Space Agency has presented the first examples of the scientific results being provided by the new X-ray observatory. Journalists had been convened to an anniversary press conference at ESA headquarters in Paris on 6 December, practically a year after launch from Kourou.
Today on its 182nd revolution around the Earth, the spacecraft itself is operating impeccably. But the essence of XMM-Newton's success lies not in the number of orbits. More significant, the data it is sending back are adding a whole new dimension to the field of X-ray astronomy. The observatory, detecting many hundreds of new X-ray sources, is greatly improving our understanding of the environment, structures and processes in the high energy Universe.
In the presence of ESA's Director of Science Prof. Roger-Maurice Bonnet and XMM-Newton's Project Scientist Fred Jansen, two of Europe's foremost X-ray astronomers presented a wide variety of the observations carried out over the past months. Prof. Johan Bleeker of the Space Research Organisation of the Netherlands, and his colleague Prof. Günther Hasinger of the Astrophysics Institute, Potsdam, explained how XMM-Newton is breaking new ground, illustrating their talks with many new X-ray "colour" images and spectra.
Fred Jansen opened proceedings with a recap on the status of the mission. Routine observations had started in June after the performance and verification phase of the science instruments. The EPIC-MOS and EPIC-pn X-ray cameras and the Optical Monitor are functioning as predicted. There has, he said, been one setback with the loss, due to a component failure in the CCD readout electronics chain of two CCD detector chips - out of a total of 18 - on the Reflection Grating Spectrometers. "We expect this problem to be contained, and the redundancy provided by the two RGS instruments means that there has been no impact on the performance." The proof of the mission's overall success to date lies in the 56 scientific papers to be published shortly in Astronomy and Astrophysics.
The guest speakers then presented a selection of science results and images. These included the subject of clusters of galaxies, the largest components in the Universe. The observatory's spectroscopy instruments have delved into the multi-million degree temperatures of the X-ray emitting gas between the galaxies in such clusters. "The extremely detailed study of the thermal environment, for example of the Coma cluster, is one of XMM-Newton's great achievements" explained Günther Hasinger. "And the X-rays we detect from the heart of such clusters is like an ultimate cry of help before matter is swallowed by a black hole."
XMM-Newton has, in its first months of observations, solved the greater part of the mystery of the origins of X-ray background emission, one of Prof. Hasinger's particular fields of interest. "The observatory is gathering all the pieces of the puzzle. We now know that 80-90% of this diffuse X-ray glow stems from very many X-ray point sources which XMM-Newton has detected." A view of the Lockman Hole was shown as an example. In this unique X-ray view into the distant Universe - comparable to a Hubble Deep Field in the optical domain - XMM-Newton has detected more than 200 individual new X-ray sources that all contribute to the X-ray background.
Supernova remnants, the remains of massive stars that have exploded, are one of Prof. Johan Bleeker's specialities "XMM-Newton has shown its great capability to unravel the composition of the interstellar matter in such remnants. This is the material that contributes to the formation of new solar systems and planets." EPIC camera views of the supernova remnant N132D highlight the distribution and relative strength of different elements, for instance oxygen and iron, in various states of ionisation. Spectra from their emission lines obtained with XMM-Newton's Reflection Grating Spectrometers provide more information about the mass and type of star that exploded and about the subsequent processes in the interstellar medium.
With unique results in such fields as the cooling flows within dense clusters of galaxies, or its analyses of X-ray emitting matter on the verge of disappearing into certain types of black holes, ESA's X-ray observatory is obliging astrophysicists to review some of their past interpretations. "We are really digging into the physics of these plasmas," said Johan Bleeker. "With its great diagnostic power, XMM-Newton is today challenging concepts that have been around for 15 years."
"You will notice that we are far from drawing definitive conclusions. Much science data still has to be analysed," said Prof. Bonnet. "But in less than a year of routine observations, X-ray astronomy as seen with the eyes of XMM-Newton is truly a 'monster astronomy' in the sense that we are dealing with huge concentrations of energy and mass. When we mention such things as neon, argon, iron, we realise that the observatory is a chemical laboratory to study the Universe."
ESA's Director of Science reminded everyone that the Agency's Integral gamma-ray mission - due to be launched in April 2002 - would be continuing to investigate these phenomena at even higher energy levels. He also evoked the next dream of the X-ray astronomers: the XEUS project, a 'telescope without a tube' with two coaligned spacecraft, one bearing the X-ray mirrors and the other the detectors.
"But for the moment," said Prof. Bonnet "it's up to XMM-Newton, and may it continue to send back such interesting science results for the next ten years."