Norbert Bartel  Ph.D. (Bonn)  Professor of Astronomy Distinguished Research Professor This e-mail address is being protected from spambots. You need JavaScript enabled to view it Personal Homepage Research Field: Astronomy and Astrophysics Research specialization: Radio astronomy; Observational tests of general relativity. Publications

Our research is focussed on galactic and extragalactic compact radio sources such as supernovae, pulsars, black hole candidates, radio stars and the powerful cores of radio galaxies and quasars. With the technique of very-long-baseline interferometry (VLBI) and a network of several large radio telescopes girdling the globe, we are able to image the areas of activity of these sources and determine their positions with an angular resolution 1,000 times better than with any optical telescope on Earth.

In particular, we make sequences of images of young, rapidly expanding supernovae, study the interaction of their shock fronts with the circumstellar medium, search for pulsars in their centers and compose the results in a "movie of an exploding star." As a spin-off, we obtain vital information for determining the distance to the host galaxy and the extragalactic distance scale. We have developed a novel data acquisition system for phase-coherent baseband recording of pulsars to complement our VLBI observations and extend our studies to searches for new millisecond pulsars and their possible companion planets and black holes. Also, we investigate the cosmological jets of energetic particles which emanate from the active centers of so-called superluminal radio galaxies and quasars with speeds that appear to be faster than the speed of light. These studies help to understand the physics of the immediate environment of these centers which are believed to be supermassive black holes.

We are involved in the support of the spaceborne Gravity Probe B mission developed by NASA and Stanford University, whose goal is to monitor the precessions of on-board gyroscopes with respect to a bright guide star to test two predictions of general relativity. With VLBI, we help to determine the guide star's proper motion with respect to distant quasars so that the precessions can be referred to the extragalactic reference frame. Also, we determine with VLBI the positions, proper motions and distances of pulsars, to aid in calibrating the dispersion-based galactic distance scale and improving the tie between the extragalactic and solar-system reference frames. Such a tie will become important for planetary spacecraft navigation and will allow another accurate test of general relativity.