Many astronomical objects emit large-scale jets of particles which radiate radio waves, visible light, X-rays and so on. The way in which these jets are formed, so that particles are "collimated", i.e. move in the same direction, are not fully understood. Approaches so far rely on numerical simulations, or use Newton's theory of gravity. Einstein's theory of gravity, general relativity, should be used but is harder to apply. We succeeded in developing a simple model for collimation in general relativity using only the geometric properties of rotating black holes.
The objects themselves form by collapse of large gas clouds under gravity. This too should be studied in general relativity, but the effects of radiation and dissipation (essentially friction) have to be included. We aimed to study the temperature effects in one such model, and how the resulting body would shine. This work is ongoing.
Finally we wanted to look at other types of collapse which might give the first exactly described case for the formation of gravitational waves. By considering possible ways to do this, we developed a approach which we believe will achieve it in the near future.