English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Gas-phase molecules in cometary atmospheres (comae) originate primarily from(1) outgassing by the nucleus, (2) sublimation of icy grains in thenear-nucleus coma, and (3) coma (photo-)chemical processes. However, themajority of cometary gases observed at radio wavelengths have yet to be mapped,so their production/release mechanisms remain uncertain. Here we presentobservations of six molecular species towards comet 46P/Wirtanen, obtainedusing the Atacama Large Millimeter/submillimeter Array (ALMA) during thecomet's unusually close (~0.1 au) approach to Earth in December 2018.Interferometric maps of HCN, CH3OH, CH3CN, H2CO, CS and HNC were obtained at anunprecedented sky-projected spatial resolution of up to 25 km, enabling thenucleus and coma sources of these molecules to be accurately quantified. TheHCN, CH3OH and CH3CN spatial distributions are consistent with production bydirect outgassing from (or very near to) the nucleus, with a significantproportion of the observed CH3OH originating from sublimation of icy grains inthe near-nucleus coma (at a scale-length $L_p=36\pm7$ km). On the other hand,H2CO, CS and HNC originate primarily from distributed coma sources (with $L_p$values in the range 550-16,000 km), the identities of which remain to beestablished. The HCN, CH3OH and HNC abundances in 46P are consistent with theaverage values previously observed in comets, whereas the H2CO, CH3CN and CSabundances are relatively low.

Gas Sources from the Coma and Nucleus of Comet 46P/Wirtanen Observed Using ALMA