ESA hosts major international X-ray symposium

In the two years since ESA's XMM-Newton and NASA's Chandra space telescopes opened their eyes to the X-ray Universe, the world's X-ray astronomers have been busy analyzing and interpreting the data from both observatories. This week the XMM-Newton and Chandra scientific communities are meeting in the Netherlands for perhaps the most important symposium since the two observatories were launched in 1999.

The response to calls for papers to be presented at the 'New Visions of the X-ray Universe in the XMM-Newton and Chandra era' symposium, which will be hosted this week by ESA's Space Research and Technology Center (ESTEC) has been phenomenal. More than 300 participants are expected to attend. 121 oral presentations and 235 poster presentations are scheduled. The symposium program with its 340 abstracts weighs in at a hefty 380 pages!

"The symposium is certainly the event of the year for X-ray astronomers," says Philippe Gondoin, a member of the local organizing committee. "It is also the first ever conference with a global overview of the results of the two major missions, XMM-Newton and Chandra, with contributions from other X-ray satellites such as BeppoSAX, RXTE and ASCA."

Better instruments...

In comparison with their predecessors, the XMM-Newton and Chandra observatories combine much larger collecting areas - which enables them to capture many more elusive X-ray photons coming from distant sources - with higher spatial and spectral resolutions, thus producing more precise images and spectra of a variety of celestial objects.

X-ray astronomers are now able to perform detailed morphological studies, spectral imaging and medium- to high-resolution spectroscopy on a wide variety of X-ray sources at a level of detail and accuracy unavailable until now.

...and surprising science

"Before launch, we were forecasting that XMM-Newton and Chandra would be 'lifting the veil' on the mysteries of the X-ray Universe," says Fred Jansen, ESA's XMM-Newton project scientist. "A nice expression but in practice it turns out to have underestimated things. With the two observatories breaking so much new ground, we can say today that they have been 'tearing the curtains down' to investigate the innermost processes at work in this high-energy Universe."

The aim of the 'New Visions' symposium is to provide a coherent view of the recent progress in this area of astrophysics. Using the power of the imagers and spectrographs aboard today's observatories, investigators are discovering that in many cases the physics in violent and distant parts of the Universe, and much closer to Earth, is more complex than earlier predictions had anticipated.

"Every new X-ray mission provides dramatic surprises, but with our new generation telescopes, we are being astounded practically on a daily basis," says Dr Martin Weisskopf, NASA project scientist for Chandra. "For instance, the recent discovery, with Chandra, of X-ray emission from at least two of the moons of Jupiter."

"XMM-Newton, for its part, is seriously challenging previous models about black holes and their environment in almost every instance where we encounter these," says Fred Jansen. "We are seeing that the physical processes involved in accretion disks, for example, are far more complicated than we thought. It is also the case that the thermal and dynamical behavior of gas near the core of clusters of galaxies is vastly different than hitherto observed. XMM-Newton has equally surprised us by observing new clusters of galaxies in unexpected numbers. We have analyses with great accuracy the abundance of elements in several active galactic nuclei, and we have gathered X-rays coming from the remotest of all known quasars, an object present 'only' a billion years after the Big Bang. All in all, XMM-Newton is clearly putting its mark on 21st century astrophysics."

The next generation

The ESTEC symposium will provide many other examples of today's greater understanding of X-ray emitting objects. Yet with a certain time lapse between the moment an observation is carried out, the data analysis and the publication of the results, much of the science being provided by XMM-Newton and Chandra is still to come. The project scientists of the two observatories have also established new joint observation possibilities which could also produce surprising results.

If the Chandra and XMM-Newton satellites and their instruments continue to stand up to the wear and tear of space, the future of X-ray astronomy is assured. Proposals for the next generation of X-ray telescopes, like ESA's Xeus or the USA's Constellation-X, will also be presented at the 'New Visions' symposium.