Explore Alliance Presents: How Do You KNOW? – Episode #26: 'Quenched Galaxies'

We normally think of galaxies as some of the largest, brightest structures in the universe – but that isn’t always true. It is star formation that makes galaxies bright. Star forming regions with abundant gas form emission nebulae, dusty regions form reflection nebulae, and the high density regions of gas and dust in a galaxy’s disk for the spiral arms that most of us are familiar with. Spiral arms are regions where density waves compress the existing gas and dust resulting in new star formation. It is these large, new, blue stars that create the light that we normally see in galaxies such as Andromeda, Triangulum, the Whirlpool and others.

Dr. Barth walks us through Hubble's discovery of the expansion, Einstein's theory of using gravity to focus the light of some of the most distant galaxies observable in the universe. 

The activities and materials provided free for the How Do You Know? program are based upon Dr. Barth’s award-winning book: Astronomy For Educators. This book is used as a resource in more than 5,700 schools across the United States and in more than 50 countries world wide. The book is published as an Open Educational Resource Text by the University of Arkansas Library Press.