Khan Academy Static

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.

17316_Space_weather_Storms_from_the_Sun.html

17318_Neil_deGrasse_Tyson_on_Finding_Krypton.html

17317_Interferometry_Sizing_up_the_Stars.html