Explorations: An Introduction to Astronomy (Arny), 7th Edition

Chapter 13: Measuring the Properties of Stars

Thought Questions

1
Using the method of parallax, what observational result would disprove that Proxima Centauri is the closest star to Earth?
2
Would it be easier to measure a star's parallax from Pluto? Why?
3
Astronomers can directly measure the diameters of a few nearby, large stars using interferometry (see figure 13.8). We might wonder why interferometry is necessary. Looking at many of the images in this book, the stars do not look like points. Why can't you use a simple photograph of Betelgeuse (like fig. 13.4) to determine its size?
4
The spectra of a B-type star and an M-type star feature different absorption lines from different elements and molecules (see fig. 13.14). Is this a result of a difference in the composition or the temperature of the star's surface? Explain.
5
When we observe spectroscopic binaries, we often do not know how the plane of the orbit is oriented to our line of sight. How will the Doppler shift change if the same orbit is oriented edge-on, face-on, or somewhere in between?
6
Redraw the brightness vs. time plot for the stars in figure 13.19 as it would appear if the smaller star were a red M-type star and the larger star were a yellow giant.
7
How could you tell the difference between a visual binary with a one-year orbit and a star moving as a result of parallax?
8
If instead of plotting luminosity vs. temperature to make an H-R diagram, we made a plot of stars' distances vs. temperatures, what sort of pattern would we find?
9
Suppose you are placing a star on an H-R diagram. Using a telescope you note a red star of apparent magnitude 3. What else would you need to know?
10
Explain the difference between luminosity and brightness. In what way is this similar to the difference between force and pressure?
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