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ASTRONOMY

ASTRONOMY. Chapter 35 Galaxies and the Expanding Universe. Hubble’s Law. In 1929, Edwin Hubble announced that: Distant galaxies are all moving away from us; and The faster the galaxy is moving away, the more distant it is. The implications of this were: The universe is expanding

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ASTRONOMY

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  1. ASTRONOMY Chapter 35 Galaxies and the Expanding Universe

  2. Hubble’s Law • In 1929, Edwin Hubble announced that: • Distant galaxies are all moving away from us; and • The faster the galaxy is moving away, the more distant it is. • The implications of this were: • The universe is expanding • There is a direct relationship between distance and amount of redshift (= speed)

  3. Hubble’s Law

  4. Hubble’s Law • This is known as Hubble’s Law. • The proportionality constant is know as Hubble’s constant. • Initially, there was considerable controversy over the value of Hubble’s constant.

  5. Hubble’s Law

  6. How Do We Measure the Universe • Primary Distance Indicators • Cepheid variables • Trigonometric parallax • Secondary Distance Indicators • Distribution of brightness of planetary nebulae • Fluctuations in brightness in the image of a galaxy • Tertiary Distance Indicators • Type Ia Supernovae

  7. The Hubble Constant • Measurements are constantly being refined • Since Hubble, values have ranged from about 55 to 100. • In 2002 (Publish date of our book) the accepted value was 72 • In December of 2012, the most recent measured value is 69.32 ±0.80 km/sec/Mpc.

  8. Distant Galaxies • It was expected that the most distant galaxies would be slower than predicted by Hubble’s law. • They are actually going faster! • Can the universe be accelerating?

  9. The 3-Dimensional Universe • Looking through a telescope gives a two-dimensional image of the sky. • Applying Hubble’s Law to this gives us the third dimension. • From these results, we find galaxies are located on the sides of bubbles, like the soap suds in a sink • Great voids are surrounded by sheets of galaxies

  10. The 3-Dimensional Universe

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