Professor Merrifield discusses motorways and stars - but says only a little about Messier 25 itself! More Messier Object videos: http://bit.ly/MessierObjects Includes discussion of the Baade-Wesselink Method and cepheid variable stars. Green Flash: https://www.youtube.com/watch?v=LWw8z75AXwU Deep Sky Videos website: http://www.deepskyvideos.com/ Twitter: https://twitter.com/DeepSkyVideos Facebook: http://www.facebook.com/DeepSkyVideos More about the astronomers in our videos: http://www.deepskyvideos.com/pages/contributors.html Made possible by: The University of Nottingham and The University of Sheffield. Video by Brady Haran