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 Plus annual

Presents the access of premium content as premium feature

Premium Content

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 annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In previous, very deep, optical images of NGC 7293 both a feature that hasthe morphology of a bow-shock and one with that of a jet were discovered in thefaint 40 arcmin diameter halo of the nebula. Spatially resolved longslitprofiles of the Halpha and [N II] 6548, 6584 A nebular emission lines from bothfeatures have now been obtained.  The bow-shaped feature has been found to have Halpha radial velocities closeto the systemic heliocentric radial velocity, -27 km/s, of NGC 7293 and isfaint in the [N II] 6548, 6584 A emission lines. Furthermore, the full width ofthese profiles matches the relative motion of NGC 7293 with its ambientinterstellar medium consequently it is deduced that the feature is a realbow-shock caused by the motion of NGC 7293 as it ploughs through this medium.The proper motion of the central star also points towards this halo featurewhich substantiates this interpretation of its origin.  Similarly [N II] 6584 A line profiles reveal that the jet-like filament isindeed a collimated outflow, as suggested by its morphology, at around 300 km/swith turbulent widths of around 50 km/s. It's low Halpha/[N II] 6548, 6584 Abrightness ratio suggests collisional ionization as expected in a high-speedjet.

The bow-shock and high-speed jet in the faint, 40 arcmin diameter, outer halo of the evolved Helix planetary nebula (NGC 7293)