I am a Professor in the Astrophysics group at University College London, and a former (2012) Ernest Rutherford Fellow.  Prior to UCL, I was a Senior Fellow at the Institute of Astronomy in Cambridge, and held postdoctoral positions at the University of Leicester and Gemini Observatory North.  My doctoral research was carried out at the University of California, Los Angeles.

My main research activity is digging up evidence of terrestrial planetary systems at stellar corpses known as white dwarfs. One might not expect to find the surviving planetary systems around dead stars, but the universe is full of surprises. In fact, it is likely we will learn more about extrasolar terrestrial planets using white dwarfs than via any other method. This is because cool white dwarfs have pure hydrogen and helium atmospheres, and those stars with rocky planetary systems can become polluted by small yet detectable amounts of heavy elements, such as metals. We can use this metal pollution to measure the composition of the rocky planetary material, and even identify water.

I use the Hubble and the Spitzer Space Telescopes to analyze the rocky debris around white dwarfs; the current picture is that they externally polluted with heavy elements from tidally destroyed asteroids.  The parent bodies descend from large and differentiated objects, and these may be leftover planetary building blocks or fragments of major planets.  The compositions measured to date are similar to the material found in the inner Solar System (i.e. like Earth!). Currently, we estimate that at least 20-30% of all white dwarfs harbor terrestrial planetary system remnants. Relevant publications and press releases can be found below.