Channel: DeepSkyVideos

Category: Science & Technology

Tags: messier 18m18rotationastronomygalaxy

Description: Messier 18 (aka NGC 6613) --- Featuring Dr Meghan Gray from the University of Nottingham. More links and info in full description ↓↓↓ CORRECTION: spiral arm patterns are thought to be due to density waves travelling through the disk. The statement in the video that the stars interior to the Sun’s galactic radius move more quickly was missing the important phrase 'relative to the spiral arm pattern speed'. Overall of course, the actual circular velocity of stars around the centre of the galaxy is remarkably constant out to large radii as with almost all spiral galaxies: leading to the important deduction that the stellar mass of the galaxy is embedded in a larger halo of ‘dark matter’. More Messier objects: bit.ly/MessierObjects Deep Sky Videos website: deepskyvideos.com Twitter: twitter.com/DeepSkyVideos Facebook: facebook.com/DeepSkyVideos More about the astronomers in our videos: deepskyvideos.com/pages/contributors.html Supported by the University of Nottingham Back us on Patreon: patreon.com/deepskyvideos Videos by Brady Haran Editing in this video by James Hennessy