Research

My main research interest is in the formation and evolution of planetary nebulae, in particular the role played by binary stars in these objects.

Planetary nebulae (PNe) are the remnants of dying intermediate mass stars. They display a spectacular range of colours and shapes, and are some of the most startlingly beautiful objects in the night sky. Those shown here are just a selection (note, some aren't PNe but other forms of astrophysical nebulosity).

Possibly the biggest missing piece in the PN puzzle is how they form such strikingly aspherical shapes. One of the prime suspects in this CSI (CircumStellar Investigation) is binarity. It is believed that if the star that formed the nebula has a close-binary partner, then this could result in the formation of a bipolar nebula. If this `binary hypothesis' is correct, then all PNe with binary central stars should display some degree of bipolarity, and most importantly the symmetry axis of this bipolar structure will lie perpendicular to the plane in which the binary orbits.

My research tackles this problem from two directions. Firstly, finding and characterising new binary central stars using time-resolved photometry and, secondly, determining the structures of the host PNe. This is much more difficult that it might sound, as we can only look at the PNe from a single direction (from Earth), and this means we can sometimes become confused depending on the orientation of the nebula to our line of sight. For example, a cylindrical nebula viewed end-on will look circular or spherical. To resolve this degeneracy between shape and orientation, I construct 3-D spatio-kinematic models of each PNe based on high-resolution, spatially resolved spectroscopy and deep, narrowband imagery. The parameters derived from these models can then be compared to those of the central binary to assess the influence of the binary in the shaping of its host PNe.