Download homework assignment 3

Astronomy 100
Name:
Homework 3
Due Monday, April 22, 2013 at 5 p.m., either electronically or on paper.
1. Most astronomy textbooks use planets orbiting the Sun to illustrate the relevance of
Kepler’s third law of planetary motion. In a class on stars and galaxies, describe a more
relevant example of Kepler’s third law (i.e., where will we use this law?).
2. There’s a lot of words on pages 1 and 2 about the concept of parallax. Let’s reduce it
to one sentence – complete the following sentence: “Over the course of half a year, a
nearby star will appear…
(You are welcome to formulate your own sentence, but it should convey what parallax is
without resorting to diagrams.)
3. In section 1.2, the idea of a star’s luminosity is introduced. The text strongly implies
that the luminosity is a measure of brightness (i.e., how much light the star gives off).
But doesn’t a star also give off heat? Sure. So why is luminosity restricted to the
brightness of a star?
4. What’s the difference between the apparent magnitude of a star and the absolute
magnitude of a star? Which one is used to calculate other characteristics (like
luminosity) of a star?
5. Draw a diagram of a spectroscopy experiment. Your drawing must include a labeled
“source”, “sample” and “detector”. For extra credit, use colored pencils to indicate what
happens to the different wavelengths of light from the source that allows us to
understand characteristics of the sample.