https://phys.org/news/2018-06-nanodiamonds-responsible-mysterious-source-microwaves.html

Until now, the most likely culprit for this microwave emission was thought to be a class of organic molecules known as polycyclic aromatic hydrocarbons (PAHs) - carbon-based molecules found throughout interstellar space and recognized by the distinct, yet faint infrared (IR) light they emit. Nanodiamonds—particularly hydrogenated nanodiamonds, those bristling with hydrogen-bearing molecules on their surfaces—also naturally emit in the infrared portion of the spectrum, but at a different wavelength.

A series of observations with the National Science Foundation's Green Bank Telescope (GBT) in West Virginia and the Australia Telescope Compact Array (ATCA) has—for the first time—homed in on three clear sources of AME light, the protoplanetary disks surrounding the young stars known as V892 Tau, HD 97048, and MWC 297. The GBT observed V892 Tau and the ATCA observed the other two systems.