what is a galaxy?
TRANSCRIPT
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What does it consist?
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Milky Way-“Galaxies kuklos”
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Galileo -Numerous stars
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18th century-William and Caroline Herschel
- Mapped the distances of stars
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1781-Charles Messier
- Cataloged various nebulae
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20th century-Harlow Shapely
- Measures the distributions and locations of globular star clusters.
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1924- Edwin Hubble
-Resolved that the spiral nebulae had structures and stars- CEPHEID VARIABLES.
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II. FORMATION AND EVOLUTION
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Ideas about the origins and evolutions:
• collapsing dust clouds = formation of galaxies
• collisions between galaxies
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Two assumptions:
1. Filled with hydrogen and helium
2. Some areas were slightly denser than others
EARLY UNIVERSE THEORIES
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Two factors:
• Angular momentum (degree of spin)
• Cooling
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III. DISTRIBUTION OF GALAXIES
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INTERGALACTIC MEDIUM
Space between galaxies and clusters of galaxies
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THE DOPPLER EFFECT
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Messier 32: a dwarf elliptical (E2) satellite galaxy of the Andromeda Galaxy
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Messier 87: giant elliptical (E1) at the Virgo Cluster's core. It has grown very large by ``eating'' other galaxies.
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NGC 2997: a large face-on spiral galaxy (Sc)
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Messier 81: a large spiral galaxy (Sb).
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The Triangulum Galaxy (=M 33): a small spiral galaxy (Scd) in the Local Group
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NGC 1365: a barred spiral galaxy (SBbc)
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NGC 3351 (=M 95): a barred spiral galaxy (SBb).
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Messier 82: a starburst galaxy
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V. PARTS OF A GALAXY
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