Galaxies are the basic building blocks of the universe. Even in a tiny patch of sky, many hundreds can be seen. By surveying such regions, astronomers estimate that there may be 100 billion galaxies in the observable universe. These galaxies are not uniformly spread through space--they commonly occur in pairs, groups, clusters, and superclusters. The articles and videos in this tutorial depict the different types of galaxies in our Universe, and the interactions between them. The final video in this tutorial looks at how one of the world's largest telescopes is bringing distant galaxies into view.
The human eye can see about 6,000 stars in the night sky. Photographs reveal millions more in every direction. All of these stars reside in our Milky Way galaxy. But they are just a tiny fraction of the several hundred billion stars in our galaxy alone. Counting all the stars in all the galaxies, there are perhaps a hundred billion billion stars in the observable universe. The videos in this tutorial show the tumultuous surface of our Sun, star systems in all their diversity, and the lifecycles of distant stars--from their birth in star clusters to the deaths of high-mass stars in spectacular explosions called supernovas.
The Sun, an unremarkable star, holds in orbit a system of planets. If most Sun-like stars have planets, then there should be billions of planets in our Milky Way Galaxy. Numerous other planetary systems have already been detected, many with configurations quite different than that of our solar system. The videos in this tutorial explore planetary systems, moving from those in our galactic neighborhood to those that orbit distant stars. These videos and articles survey the diverse planets in our solar system, from the forces that shape their surfaces to ring systems and moons to the search for the building blocks of life. Last is a documentary about how astrophysicists are using new tools to study the chemical characteristics of these faraway worlds.
The universe is all the matter, energy, and space that exist. We can observe only a part of it--the observable universe. The entire, universe, including the part we cannot see, may be infinite. The observable universe contains as many as 100 billion galaxies and extends a billion light-years in every direction. The first five videos in this tutorial depict the different types of galaxies in our Universe, including spiral, giant and dwarf ellipticals. The interactions between these galaxy types are the subject of the five time-lapse simulations that follow. The last two videos describe two galactic phenomena: the Phoenix galaxy, which produces stars faster than any other known galaxy; and the formation of an elliptical galaxy 11 billion years ago, when two massive spiral galaxies merged.
All video content by Khan Academy is under their license: CC by NC SA
Website created using Khan Academy Static Downloader