UCL News


Space scientists hold first conference on x-ray specs

14 February 2003

More than 70 scientists from around the world gathered at UCL's Mullard Space Science Laboratory in October 2002 to share and review theories, results and analysis techniques based on data received from the two major x-ray astronomy satellites.

XMM-Newton in orbit The European Space Agency's 'XMM-Newton' and NASA's 'Chandra' observatories have provided data with the highest energy resolution ever attained in x-rays. This means that the astronomers can diagnose the physical properties of the sources of the x-rays, similar to DNA testing in humans.

The event, organised by Dr Graziella Branduardi-Raymont (Space & Climate Physics), was the first international workshop organised specifically to deal with high-resolution dispersive x-ray spectroscopy from all sorts of cosmic sources.

'Chandra' carries a high-resolution mirror, two imaging detectors and two sets of transmission gratings, while on 'XMM-Newton' the high resolving power of the reflection grating spectrometer is coupled to a very large collecting area. This makes it an ideal instrument for detailed spectroscopic investigations of faint and distant sources, from stars to active galaxies.

Dr Branduardi-Raymont said: "From the emission and absorption lines that we see, we can deduce temperatures, densities and chemical composition and motions of the hot and turbulent gases that emit the x-rays, be these in the coronae of stars, in the surroundings of neutron stars in binary systems or near stellar black holes, in the expanding shells of gas produced in a supernova explosion or in the cores of active galaxies."

High-resolution spectroscopy in the x-ray band has proven to be an invaluable diagnostic tool in detailed investigations of dynamics and physical structures. Until recently these could only be carried out on the closest of these sources, the Sun. Now that such observations are routinely carried out and the data distributed widely within the astronomical community, it was important for space scientists to review the results and explore the analysis techniques associated with these observations.

Dr Branduardi-Raymont said: "Much of our discussion focused on how to reconcile theory and the new data. For example, we know that at the core of many clusters of galaxies there are flows of cooling gas falling towards the centre. However, high-resolution data from 'XMM-Newton' show no evidence at all for the very cool gas expected right at the centre. Theories will have to be revised and new ideas put forward in order to make sense of what we observe."

She concluded: "As often happens when new instrumentation is introduced, surprises have shown up thick and fast. They remind us that nature is never dull, but rather more complex than we have imagined."

Image: XMM-Newton in orbit.

To find out more about the workshop use the link below.

Link: Mullard Space Science Laboratory