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

Chapter 14: Stellar Evolution

Problems

1
Sketch an H-R diagram of what you expect the evolutionary paths of a 2-M. and a 15-M. star to look like.
2
The density of a cold interstellar cloud prior to collapsing might be about 1.67 × 10-20 kg/m3. How many cubic meters of this cloud would contain enough mass to build the Sun? What is the ratio of this volume to the volume of the Sun? What is the volume of cloud required if written in cubic light-years?
3
The jets from a T Tauri star are measured to have speeds of about 300 km/sec. At this speed, how long would it take the ejected material to travel 2 light-years (similar to the jets shown in figure 14.7)?
4
Calculate the main-sequence lifetime of the Sun by first determining the rate at which it burns hydrogen (refer to chapter 12) and then dividing that rate into its core mass. I f your answer is in seconds, convert to years, given that there are about 3.2 × 107 seconds in a year.
5
Calculate the escape velocity from a red giant's atmosphere (use the formula for escape velocity from chapter 3). Assume that the star's mass is 1 M. and its radius is 100 R.. How does this compare with the speed at which a planetary nebula shell is ejected?
6
Calculate the average density of a red giant star in grams per cubic centimeter. Take the star's mass to be 2 × 1033 grams and its radius to be 3 × 1012 centimeters. How does this density compare with that of the air we breathe (about 10-3 gm/cm3)?
7
How long will it take a planetary nebula shell moving at 20 km/sec to expand to a radius of one-fourth of a light-year?
8
Calculate the Doppler shift of X-rays emitted from shocked silicon in a supernova remnant if the ejected material is moving at 5000 km/sec and the X-ray line is at 0.688 nanometers.
9
Figure 14.28 shows the H-R diagram of a star cluster. How old is it? (The dashed line is the position of the stars. The solid line is the main sequence.)
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