Tiny diamond crystals only a few atoms across are now thought to be the source of an enigmatic form of astrophysical radiation known as anomalous microwave emission (AME). AME was an unexpected discovery during the 1990s, where it was detected as a large scale foreground contamination of the cosmic microwave background. Astronomers quickly concluded that the anomalous emission was generated by rapidly rotating dust grains, but the question was: what kind of dust grain? At first we thought it might be produced by a tiny dust grain, the size of a large molecule, called a polycyclic aromatic hydrocarbon (PAH), but measurements looking for a correlation between PAHs and AME in our Galaxy came back negative. However, new observations looking at dust in the planet-forming disks around young stars produced a startling result; some of these dusty disks showed evidence for AME – but only the disks that were also known to be filled with nanometre-sized diamonds. I will talk about how we made this discovery, what a nanodiamond is and how you make one spin, and where we go from here.

Speaker: Anna Scaife