SCIE 1920U Chapter Notes - Chapter 14: Gravitational Lens, Galactic Center, Accelerating Expansion Of The Universe
Document Summary
Every object on a merry-go-round goes around the center in the same amount of time, but objects farther from the center move in larger circles, so they must move at faster speeds. The rotation curve for a merry-go-round is therefore a straight line that rises steadily with distance. Orbital speeds in our solar system decrease with distance from the sun. Each individual dot represents the orbital speed and distance from the galactic center of a particular star or gas cloud, and the curve running through the dots represents a best fit to the data. This shows most of the mass is not centered in the galaxy. There is something outside the galaxy in the halo and the total amount of this mass is more than 10 times the total mass of all the stars in the disk. Other galaxies also seem to contain vast quantities of dark matter.
