The Milky Way

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

The Milky Way Panorama

Credit: Addison Wesley

Structure of The Milky Way Galaxy

Total number of stars: few x 100 billions

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

Current View of the Milky Way

Credit: NASA/JPL/R. Hurt

Sir Frederick William Herschel 赫歇爾 (1738-1822)

48-inch reflector

DSpace@Cambridge7

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Nebulae drawn by William Herschel

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.

Credit: Pearson Prentice Hall, Inc.

Standard Candles - Cepheids 造父變星

Credit: Robert Gendler

M31 Andromeda Nebula 仙女座大星雲

Galaxy 系

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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

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