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

Some important predictions from 4 main models of spiral arm formation aretested here, using observational data acquired for the Milky Way galaxy. Manyspiral arm models (density wave, tidal wave, nuclear Lyapunov tube, or dynamictransient wave) have some consistencies with some of the observations, and someinconsistencies. Our 4 tests consist of the relative locations and relativespeeds of different arm tracers away from the dust lane, and the global armpitch angle as obtained over two Galactic quadrants and several Galactic radii,as well as the arm's continuity of shape from Galactic quadrant IV to Galacticquadrant I. In the Milky Way, an age gradient is observed from different armtracers, amounting to 12.9 +/-1.1 Myrs/kpc, or a relative speed away from thedust lane of 76 +/-10 km/s. The presence of an age gradient is predicted by thedensity waves, but is not consistent with the predictions of the tidal waves,of the nuclear Lyapunov tubes, nor of the dynamic transient recurrent waves.

The Observed Age Gradient in the Milky Way -- as a Test for theories of spiral arm structure