1. The Milky Way
The Milky Way is a prominent band of light across the sky

2. The Milky Way Panorama

3. Credit: Addison Wesley
Structure of The Milky Way Galaxy
Total number of stars: few x 100 billions

4. M51 Whirlpool Galaxy 渦狀星系
Credit: NASA and The Hubble Heritage Team (STScI/AURA)
Spiral Arm 旋臂距離：3100萬光年
直徑：3萬光年

5. Current View of
the Milky Way
Credit: NASA/JPL/R. Hurt

6. Sir Frederick William Herschel
赫歇爾(1738-1822)

7. 48-inch reflector
DSpace@Cambridge
7

8. 8
Nebulae drawn by William Herschel

9. The Leviathan of Parsonstown 帕森城海怪
The largest telescope in the 19th century, with a 1.8m mirror. It was
built by William Parsons, 3rd Earl of Rosse on his Castle in 1845.

12. Credit: Pearson Prentice Hall, Inc.
Standard Candles - Cepheids 造父變星

13. Credit: Robert Gendler
M31 Andromeda Nebula 仙女座大星雲
Galaxy 系

14. CCST9012
Our Place in the Universe
Some of the globular clusters
(circled) surrounding the Milky Way
Mt. Wilson 60-inch telescope
built in 1908
http://www.astro.caltech.edu/palomar/history.html

15. Are we at the center of the Milky Way?
• Shapely determined the distances to 69 globular clusters and mapped their
distribution in space by using the Cepheids as distance markers.
• If globular clusters were uniformly distributed in the Milky Way, then his data
suggested our Sun is not in the center but off to one side of a flat disk of stars.
http://www.aip.org/history/cosmology/ideas/island.htm
Our Sun
Center