Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 18, Problem 25E
Use the data in Appendix J to plot an H−R diagram for the brightest stars. Use the data from Table 18.3 to show where the main sequence lies. Do 90% of the brightest stars lie on or near the main sequence? Explain why or why not.
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Astronomy
Ch. 18 - How does the mass of the Sun compare with that of...Ch. 18 - Name and describe the three types of binary...Ch. 18 - Describe two ways of determining the diameter of a...Ch. 18 - What are the largest- and smallest-known values of...Ch. 18 - You are able to take spectra of both stars in an...Ch. 18 - Sketch an HR diagram. Label the axes. Show where...Ch. 18 - Describe what a typical star in the Galaxy would...Ch. 18 - How do we distinguish stars from brown dwarfs? How...Ch. 18 - Describe how the mass, luminosity, surface...Ch. 18 - One method to measure the diameter of a star is to...
Ch. 18 - We discussed in the chapter that about half of...Ch. 18 - Is the Sun an average star? Why or why not?Ch. 18 - Suppose you want to determine the average...Ch. 18 - Why do most known visual binaries have relatively...Ch. 18 - Figure 18.11 shows the light curve of a...Ch. 18 - There are fewer eclipsing binaries than...Ch. 18 - Within 50 light-years of the Sun, visual binaries...Ch. 18 - Which is easier to observe at large distances-a...Ch. 18 - The eclipsing binary Algol drops from maximum to...Ch. 18 - Review this spectral data for five stars. Which is...Ch. 18 - Which changes by the largest factor along the main...Ch. 18 - Suppose you want to search for brown dwarfs using...Ch. 18 - An astronomer discovers a type-M star with a large...Ch. 18 - Approximately 6000 stars are bright enough to be...Ch. 18 - Use the data in Appendix J to plot an HR diagram...Ch. 18 - Use the diagram you have drawn for Exercise 18.25...Ch. 18 - Use the data in Appendix I to plot an HR diagram...Ch. 18 - If a visual binary system were to have two...Ch. 18 - Two stars are in a visual binary star system that...Ch. 18 - Describe the spectra for a spectroscopic binary...Ch. 18 - Figure 18.7 shows the velocity of two stars in a...Ch. 18 - You go out stargazing one night, and someone asks...Ch. 18 - If you were to compare three stars with the same...Ch. 18 - Are supergiant stars also extremely massive?...Ch. 18 - Consider the following data on four stars: Which...Ch. 18 - If two stars are in a binary system with a...Ch. 18 - It is possible that stars as much as 200 times the...Ch. 18 - The lowest mass for a true star is 1/12 the mass...Ch. 18 - Spectral types are an indicator of temperature....Ch. 18 - We can estimate the masses of most of the stars in...Ch. 18 - In Diameters of Stars, the relative diameters of...Ch. 18 - Now calculate the radius of Sirius’ white dwarf...Ch. 18 - How does this radius of Sirius B compare with that...Ch. 18 - From the previous calculations and the results...Ch. 18 - How much would you weigh if you were suddenly...Ch. 18 - The star Betelgeuse has a temperature of 3400 K...Ch. 18 - Using the information provided in Table 18.1, what...Ch. 18 - Confirm that the angular diameter of the Sun of...Ch. 18 - An eclipsing binary star system is observed with...Ch. 18 - If a 100 solar mass star were to have a luminosity...Ch. 18 - If Betelgeuse had a mass that was 25 times that of...
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- Astronomers find that 90% of the stars observed in the sky are on the main sequence of an HR diagram; why does this make sense? Why are there far fewer stars in the giant and supergiant region?arrow_forwardIf you were to compare three stars with the same surface temperature, with one star being a giant, another a supergiant, and the third a main-sequence star, how would their radii compare to one another?arrow_forwardIn the HR diagrams for some young clusters, stars of both very low and very high luminosity are off to the right of the main sequence, whereas those of intermediate luminosity are on the main sequence. Can you offer an explanation for that? Sketch an HR diagram for such a cluster.arrow_forward
- How do stars typically “move” through the main sequence band on an HR diagram? Why?arrow_forwardDescribe how the mass, luminosity, surface temperature, and radius of main-sequence stars change in value going from the “bottom” to the “top” of the main sequence.arrow_forwardOn which edge of the main sequence band on an HR diagram would the zero-age main sequence be?arrow_forward
- If a 100 solar mass star were to have a luminosity of 107 times the Sun’s luminosity, how would such a star’s density compare when it is on the main sequence as an O-type star, and when it is a cool supergiant (M-type)? Use values of temperature from Figure 18.14 or Figure 18.15 and the relationship between luminosity, radius, and temperature as given in Exercise 18.47. Figure 18.15 Schematic HR Diagram for Many Stars. Ninety percent of all stars on such a diagram fall along a narrow band called the main sequence. A minority of stars are found in the upper right; they are both cool (and hence red) and bright, and must be giants. Some stars fall in the lower left of the diagram; they are both hot and dim, and must be white dwarfs. Figure 18.14 HR Diagram for a Selected Sample of Stars. In such diagrams, luminosity is plotted along the vertical axis. Along the horizontal axis, we can plot either temperature or spectral type (also sometimes called spectral class). Several of the brightest stars are identified by name. Most stars fall on the main sequence.arrow_forwardAccording to the text, a star must be hotter than about 25,000 K to produce an H II region. Both the hottest white dwarfs and main-sequence O stars have temperatures hotter than 25,000 K. Which type of star can ionize more hydrogen? Why?arrow_forwardYou can use the equation in Exercise 22.34 to estimate the approximate ages of the clusters in Figure 22.10, Figure 22.12, and Figure 22.13. Use the information in the figures to determine the luminosity of the most massive star still on the main sequence. Now use the data in Table 18.3 to estimate the mass of this star. Then calculate the age of the cluster. This method is similar to the procedure used by astronomers to obtain the ages of clusters, except that they use actual data and model calculations rather than simply making estimates from a drawing. How do your ages compare with the ages in the text? Figure 22.10 NGC 2264 HR Diagram. Compare this HR diagram to that in Figure 22.8; although the points scatter a bit more here, the theoretical and observational diagrams are remarkably, and satisfyingly, similar. Figure 22.12 Cluster M41. (a) Cluster M41 is older than NGC 2264 (see Figure 22.10) and contains several red giants. Some of its more massive stars are no longer close to the zero-age main sequence (red line). (b) This ground-based photograph shows the open cluster M41. Note that it contains several orange-color stars. These are stars that have exhausted hydrogen in their centers, and have swelled up to become red giants. (credit b: modification of work by NOAO/AURA/NSF) Figure 22.13 HR Diagram for an Older Cluster. We see the HR diagram for a hypothetical older cluster at an age of 4.24 billion years. Note that most of the stars on the upper part of the main sequence have turned off toward the red-giant region. And the most massive stars in the cluster have already died and are no longer on the diagram. Characteristics of Main-Sequence Starsarrow_forward
- We can estimate the masses of most of the stars in Appendix J from the mass-luminosity relationship in Figure 18.9. However, remember this relationship works only for main sequence stars. Determine which of the first 10 stars in Appendix J are main sequence stars. Use one of the figures in this chapter. Make a table of stars’ masses. Figure 18.9 Mass-Luminosity Relation. The plotted points show the masses and luminosities of stars. The three points lying below the sequence of points are all white dwarf stars.arrow_forwardAutomobiles are often used as an analogy to help people better understand how more massive stars have much shorter main-sequence lifetimes compared to less massive stars. Can you explain such an analogy using automobiles?arrow_forward
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