Natural Science - Year II
Unit 63: Hubble and Galaxies
Science Weblecture for Unit 63
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Unit 63: Galaxies and the size of the universe
For Class
- Topic area: Astronomy
- Terms and concepts to know: Galaxy, parsec, light year, Hubble tuning fork
- See history topics: Biology: Annie's Girls
Lecture:
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:
- How do computer models help us understand galactic formation?
- What role should computer models play in science?
On your own
- Check out the Hubble Telescope pictures of galaxies.
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