Nanodiamonds in protoplanetary disks could be the cause of anomalous microwave emissions

Artist's concept of nanodiamonds in a protoplanetary disk (Image courtesy S. Dagnello, NRAO/AUI/NSF)
Artist’s concept of nanodiamonds in a protoplanetary disk (Image courtesy S. Dagnello, NRAO/AUI/NSF)

An article published in the journal “Nature Astronomy” describes the detection of nanodiamonds around three newborn star systems in the Milky Way. A team of researchers led by astronomer Jane Greaves of the Welsh University of Cardiff used the Green Bank Telescope (GBT) to observe the V892 Tau system and the Australia Telescope Compact Array (ATCA) to observe the HD 97048 and MWC 297 systems obtaining the first clear detections of anomalous microwave emissions (AMEs) concluding that the nanodiamonds are their source.

An anomalous microwave emission is a weak and anomalous light at microwave frequencies observed in some regions of the Milky Way starting almost 20 years ago with peaks of tens of GigaHertz. Among the various hypotheses on the sources of those emissions, polycyclic aromatic hydrocarbons (PAHs) seemed the most likely but a new research could point finger on nanodiamonds.

Hydrogenated diamonds, meaning diamonds enriched with hydrogen atoms, hundreds of thousands of times smaller than grains of sand can naturally form in protoplanetary disks that rotate around newborn stars and form planets and other minor celestial bodies in a star system. Radio telescopes can detect the frequencies of abnormal microwave emissions, so GBT and ATCA were suitable for this type of research.

The V892 Tau, HD 97048 and MWC 297 star systems are very young so they have their protoplanetary disks. In those systems anomalous microwave emissions were detected, the first clear detections of that type coming from protoplanetary disks. These were perfect objects for an investigation that Jane Greaves compared to those of Sherlock Holmes for the need to eliminate the impossible to get to the “culprit”.

The infrared emissions from those systems match the “signature” of nanodiamonds. Other protoplanetary disks observed show the typical infrared emissions of polycyclic aromatic hydrocarbons but show no sign of anomalous microwave emissions. In short, it seems that nanodiamonds are responsible for those emissions.

The formation of nanodiamonds in protoplanetary disks is a phenomenon known better and better over time, now the instruments available have given the possibility to connect it to anomalous microwave emissions. According to astronomers, 1-2% of the carbon present in protoplanetary disks form nanodiamonds, enough to cause emissions visible many light years away.

This is a really huge amount but probably those nanodiamonds don’t have great value. It’s not only a matter of size but also of the conditions in which they form, which probably cause them to have many more flaws than the diamonds that form on Earth. In short, even if we could collect them they wouldn’t be suitable as gifts but they’re still interesting under a scientific point of view.

Leave a Reply

Your email address will not be published. Required fields are marked *