This is the twelfth lecture series of my complete online introductory undergraduate college course. This video series was used at William Paterson University and CUNY Hunter in online classes as well as to supplement in-person course material. Notes and links are present in the videos at the start of each lecture.
0:00:00 - Our Cosmic Address
0:14:51 - The Great Cosmic Distance Debate
1:06:29 - The Milky Way's Many Faces
1:35:14 - Stellar Neighborhoods: the Population I and II Stars
1:53:35 - The Galaxy's Formation, Evolution and Fate
2:13:31 - The Milky Way's Spiral Arms
2:39:57 - Dark Matter in the Milky Way and Beyond
3:24:06 - The Supermassive Black Hole at the Center of the Milky Way
(Correction: William Parsons, The Third Earl of Rosse, was Irish, not British. Apologies to the Irish viewers out there!)
Now we start the process of learning our place in space, by learning about our Cosmic Address. Where is our place in the universe? What is the scale of the Cosmic Map? After that, we learn the history of the Great Cosmic Distance Debate. The development of our understanding of our place that was just described is one of the great stories of modern science. The people of the latter part of the 19th century and the early 20th were just learning about what was out there. Their fierce debates and competitive drives were spurred on by their insatiable curiosity. We learn of great women pioneers in science, and we learn that the painstaking measurements of the distances to the nearest galaxies led to one of the most surprising findings of all time: the expansion of the universe. We then take a step back and look more closely at our home Galaxy, looking at full-sky images in many wavelengths that detail exactly what makes up our home. Next, these simple observations, combined with spectroscopic analysis gave rise to the discovery of two broad types of stars in the Milky Way, the practically-named Population I and II Stars. This gives us the basis for understanding that all stars and therefore our galaxy, changes with time. Armed with this understanding, we reach into the deep past and the deep future, as we explore the formation, evolution and fate of the Milky Way. We jump around in our discussion to the factories of star formation, the spiral arms. We show the evidence for them in our Galaxy, and we see our Galaxy as one among many. Following that, we see great anomalies in the way our Galaxy rotates, and how the spiral arm structure evolves. By studying this motion, astronomers discovered that there was something missing. A lot of stuff was missing. The Galaxy is rotating faster than it should when we take into account all the matter that emits light. We learned that most of the matter in the cosmos doesn’t interact with light at all, and was named Dark Matter. Last, we learn about the behemoth black hole residing in the core of the Milky Way. A central place of exceeding violence that’s safely placed many tens of thousands of lightyears away. The supermassive black hole at the center of the Milky Way, SGR A*, belies its presence through its influence on stars and gas clouds in its local environment. It's the nearest such black hole, and there is ample reason for us thinking it actually is such an object.