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Natural Science - Year II

Unit 63: Hubble and Galaxies

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Science Weblecture for Unit 63

This Unit's Homework Page History Lecture Science Lecture Lab Parents' Notes

Unit 63: Galaxies and the size of the universe

For Class


Classifying Galaxies

Distances to Galaxies

Galaxies can be grouped into classes by their shape and energy output. Classifications in the last four decades have changed as our understanding of observational limitations changed.

Take a look at the chart of the the distance ladder at the David Darling Encyclopedia site. Follow links to explain terms like "moving cluster" and "main-sequence fitting" methods.

  • Why are different methods necessary to establish distances to objects like stars and galaxy clusters?
  • What are some of the problems with using the different methods?
  • What would happen to our estimates of distances if we discovered a consistent error in radar ranging? A consistent error in Main-Sequence Fitting?

The Hubble tuning Fork

Read about the the classification of galaxies using Hubble's "tuning fork".

  • What major characteristics did Hubble use to classify galaxies?
  • What type of galaxy is our home galaxy (the Milky Way)?
  • What are some of the problems in classifying galaxies?
  • What do the types of galaxies indicate about galactic formation?

Study/Discussion Questions:

On your own