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Anomalous microwave emission from spinning nanodiamonds around stars

Greaves, J. S. ORCID:, Scaife, A. M. M., Frayer, D. T., Green, D. A., Mason, B. S. and Smith, A. M. S. 2018. Anomalous microwave emission from spinning nanodiamonds around stars. Nature Astronomy 2 , pp. 662-667. 10.1038/s41550-018-0495-z

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Several interstellar environments produce anomalous microwave emission (AME), with brightness peaks at tens-of-gigahertz frequencies1. The emission’s origins are uncertain; rapidly spinning nanoparticles could emit electric-dipole radiation2, but the polycyclic aromatic hydrocarbons that have been proposed as the carrier are now found not to correlate with Galactic AME signals3,4. The difficulty is in identifying co-spatial sources over long lines of sight. Here, we identify AME in three protoplanetary disks. These are the only known systems that host hydrogenated nanodiamonds5, in contrast with the very common detection of polycyclic aromatic hydrocarbons6. Using spectroscopy, the nanodiamonds are located close to the host stars, at physically well-constrained temperatures7. Developing disk models8, we reproduce the emission with diamonds 0.75–1.1 nm in radius, holding ≤1–2% of the carbon budget. Ratios of microwave emission to stellar luminosity are approximately constant, allowing nanodiamonds to be ubiquitous, but emitting below the detection threshold in many star systems. This result is compatible with the findings of similar-sized diamonds within Solar System meteorites9. As nanodiamond spectral absorption is seen in interstellar sightlines10, these particles are also a candidate for generating galaxy-scale3 AME.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Publisher: Nature Publishing Group
ISSN: 2397-3366
Date of First Compliant Deposit: 12 June 2018
Date of Acceptance: 11 May 2018
Last Modified: 08 Dec 2023 18:10

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