The Milky Way in visible light

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The Milky Way in visible light
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near-IR (2Mass) 1500 LY
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near-IR (2Mass) 1500 LY elliptical
stellar orbits in central arcsecond
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Active Galactic Nuclei
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(No Transcript)
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• The Hertzsprung-Russel diagram
• a.k.a. HR diagram
• Vertical axis L
• Horiz. axis Ts

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• The Hertzsprung-Russel diagram
• a.k.a. HR diagram
• Vertical axis L
• Horiz. axis Ts

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• The Hertzsprung-Russel diagram
• a.k.a. HR diagram
• Vertical axis L
• Horiz. axis Ts

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• The Hertzsprung-Russel diagram
• a.k.a. HR diagram
• Vertical axis L
• Horiz. axis Ts

10

• The Hertzsprung-Russel diagram
• a.k.a. HR diagram
• Vertical axis L
• Horiz. axis Ts

11

• The Hertzsprung-Russel diagram
• a.k.a. HR diagram
• Vertical axis L
• Horiz. axis Ts

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• The Hertzsprung-Russel diagram
• a.k.a. HR diagram
• Vertical axis L
• Horiz. axis Ts

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A main sequence G2 star, like the Sun, makes a
good standard candle
Certain types of giant stars, especially the
so-called Cepheid variables, are also used as
standard candles
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Edwin Hubble found Cephieds in Andromeda galaxy -
1923
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Another type of standard candle type 1a
supernovae
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Except for the closest few galaxies, they are all
moving away from us (fast!)