class18a - Friday, Oct. 10 Syllabus, class notes, and...

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Friday, Oct. 10 Syllabus, class notes, and homeworks are at: www.as.utexas.edu courses AST 301, Lacy Reading for next week: chapter 9 The Wednesday help session is in GRG 424 at 5:00 (for the entire semester).
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Topics for this week How do astronomers use parallax to measure the distances to stars? Why does parallax vary inversely with distance? Describe and explain the relationship between a star’s apparent brightness (or flux), its absolute brightness (or luminosity), and its distance from us. Describe and explain the relationship between a star’s luminosity, its radius, and its temperature, and how this relationship is used to measure radii of stars. Sketch an H-R diagram, showing the location of main sequence stars, red giants, and white dwarfs. Explain how astronomers measure masses of stars. Describe how the luminosities of main sequence stars are related to their masses.
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Parallax and Distance You judge the distance to objects (depth perception) from the fact that your two eyes view an object from two different locations, so have to look in different directions to look at an object. The different direction to an object from different positions is called parallax. Astronomers use the change in the direction to a star
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class18a - Friday, Oct. 10 Syllabus, class notes, and...

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