Determining the Scale and Structure
of our Galaxy
In the early part of this century, the Dutch Astronomer Kapteyn used
parallax and stellar motions to get a physical SCALE of the galaxy
(which was very close to correct!).
However, he still placed the Sun near its center.
Why?? Dust again..
| About the same time, American Astronomer Shapley, used distance estimates to Globular Clusters to get a different scale and structure to our Galaxy: |
|
He argued that these massive clusters must be orbiting the center of our
Galaxy, which was NOT at the position of the Sun (which was correct!).
He unfortunately overestimated the total SCALE of the galaxy.
Why did he get the scale wrong?? Dust again..
We must learn about Variable Stars to understand why.