AS102 Final: If we knew the location of every star in the galaxy at any given time we could apply Kepler
Document Summary
If we knew the location of every star in the galaxy at any given time we could apply. Kepler"s laws to find the total mass of the galaxy. However, interstellar dust obscures our view of disk stars beyond a few thousand ly, making it difficult to measure stellar velocities. Instead we use radio spectroscopy to see through the dust and to build up a map of the galaxy. From this astronomers make a diagram called the rotation curve that plots orbital velocity versus distance from the centre of the galaxy. In this diagram from your textbook this is labelled as. It was expected that the rotation curve for our galaxy would rise sharply at first (as the red curve does) because there are so many stars in the bulge in the middle of the galaxy. The curve should continue to drop down lower and lower as the star population peters out.
