Interferometry in the infrared provides unique insights into many types of astrophysical objects such as young stellar objects, stars in late evolutionary stages and active galactic nuclei. In particular, it is now possible to create aperture-synthesis images in the near-infrared. These images can be obtained with a spectacular resolution by combining (interfering) the light from the telescopes of interferometers such as ESO's Very Large Telescope Interferometer (VLTI). This method is able to reconstruct images with a resolution equivalent to the theoretical resolution of a telescope with a diameter of 200 m. Interferometry in the spectral ranges of 1-2 and 7-13 microns can simultaneously provide a high spectral and high spatial resolution, reaching an angular resolution of a few milli-arcseconds.
Even though electromagnetism is one of the four fundamental forces of nature, little is known about how large-scale magnetic fields are generated in galaxies. Sensitive broadband radio synchrotron polarization observations of emission from the galaxies themselves and Faraday Rotation Measure of background radio sources behind them provide us with the best chance to understand the processes that generate galactic-scale magnetic fields.
Stars mostly form as part of a whole cluster of stars. In this phase the young stars are surrounded by a gas/dust disc, which under favourable circumstanes provides the material for the formation of a planetary system. In these young clusters the stars are so densely packed that close fly-bys are a common event. The acting gravitational forces between the stars are so strong that they potentially disturb the discs and just form planetary systems. Computer programs are developed allowing to simulate this situation on high-performance computers. Thus it is possible to determine in how far the cluster environment influences star and planet formation.