The Sky at Night team go cosmic ghost-hunting, looking for hidden objects across the universe that we can't see, but which astronomers and scientists still believe are out there.

In this Sky at Night special, the team talk to Dr Nicola Fox, NASA's head of science, whose life began in the UK. Presenter Chris Lintott chats to Nicky about her early years growing up in Hitchin in Hertfordshire and discovers how she fell in love with the stars. Maggie Aderin-Pocock takes Nicky on a trip down memory lane. Both women studied physics at Imperial College London from the late 80s to early 90s. As they revisit familiar haunts, they discuss their experiences, and Maggie finds out about Nicky's love of astrophysics, the challenges she overcame and how she landed a dream job at NASA.