Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 20, Problem 8E
What causes reddening of starlight? Explain how the reddish color of the Sun’s disk at sunset is caused by the same process.
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Astronomers use two basis properties of stars to classify them. These two properties are luminosity and surface temperature. Luminosity usually refers to the brightness of the star relative to the brightness of our sun. Astronomers will often use a star’s color to measure its temperature. Stars with low temperatures produce a reddish light while stars with high temperatures shine with a brilliant blue—white light. Surface temperatures of stars range from 3000o C to 50,000o C. When these surface temperatures are plotted against luminosity, the stars fall into groups. Using the data similar to what you will plot in this activity, Danish astronomer Ejnar Hertzsprung and United States astronomer Henry Norris Russell independently arrived at similar results in what is now commonly referred to as the HR Diagram.
Procedures:1. Read the Background Information
2. On the graph paper provided. Place a number next to the star according to its luminosity and surface temperature listed in the data…
Chapter 20 Solutions
Astronomy
Ch. 20 - Identify several dark nebulae in photographs in...Ch. 20 - Why do nebulae near hot stars look red? Why do...Ch. 20 - Describe the characteristics of the various kinds...Ch. 20 - Prepare a table listing the different ways in...Ch. 20 - Describe how the 21-cm line of hydrogen is formed....Ch. 20 - Describe the properties of the dust grains found...Ch. 20 - Why is it difficult to determine where cosmic rays...Ch. 20 - What causes reddening of starlight? Explain how...Ch. 20 - Why do molecules, including H2 and more complex...Ch. 20 - Why can’t we use visible light telescopes to study...
Ch. 20 - The mass of the interstellar medium is determined...Ch. 20 - Where does interstellar dust come from? How does...Ch. 20 - Figure 20.2 shows a reddish glow around the star...Ch. 20 - If the red glow around Antares is indeed produced...Ch. 20 - Even though neutral hydrogen is the most abundant...Ch. 20 - The terms H II and H2 are both pronounced “H two.”...Ch. 20 - Suppose someone told you that she had discovered H...Ch. 20 - Describe the spectrum of each of the following: A....Ch. 20 - According to the text, a star must be hotter than...Ch. 20 - From the comments in the text about which kinds of...Ch. 20 - One way to calculate the size and shape of the...Ch. 20 - New stars form in regions where the density of gas...Ch. 20 - Thinking about the topics in this chapter, here is...Ch. 20 - Stars form in the Milky Way at a rate of about 1...Ch. 20 - The 21-cm line can be used not just to find out...Ch. 20 - Astronomers recently detected light emitted by a...Ch. 20 - We can detect 21-cm emission from other galaxies...Ch. 20 - We have said repeatedly that blue light undergoes...Ch. 20 - Suppose that, instead of being inside the Local...Ch. 20 - Suppose that, instead of being inside the Local...Ch. 20 - A molecular cloud is about 1000 times denser than...Ch. 20 - Would you expect to be able to detect an H II...Ch. 20 - Suppose that you gathered a ball of interstellar...Ch. 20 - At the average density of the interstellar medium,...Ch. 20 - Consider a grain of sand that contains 1 mg of...Ch. 20 - H II regions can exist only if there is a nearby...Ch. 20 - In the text, we said that the five-times ionized...Ch. 20 - Dust was originally discovered because the stars...Ch. 20 - How would the density inside a cold cloud (T=10K)...Ch. 20 - The text says that the Local Fluff, which...
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- Spectral types are an indicator of temperature. For the first 10 stars in Appendix J, the list of the brightest stars in our skies, estimate their temperatures from their spectral types. Use information in the figures and/or tables in this chapter and describe how you made the estimates.arrow_forwardA star has a surface temperature of T = 10,000 K and a radius three times that of the Sun, R = 3R (recall that symbolizes the Sun). What is its luminosity, L, in units of solar luminosities, L ? Give your answer to three significant figures. answer, expressed in solar luminosities, tells how many times more luminous this star is than the Sun.arrow_forward57. Solar Power Collectors. This problem leads you through the calculation and discussion of how much solar power can in principle be collected by solar cells on Earth. a. Imagine a giant sphere with a radius of 1 AU surrounding the Sun. What is the surface area of this sphere, in square meters? (Hint: The formula for the surface area of a sphere is 4rr2.) b. Because this imaginary giant sphere surrounds the Sun, the Sun's entire luminosity of 3.8 × 1020 watts must pass through it. Calculate the power passing through each square meter of this imaginary sphere in watts per square meter. Explain why this number represents the maximum power per square meter that a solar collector in Earth orbit can collect. c. List several reasons why the average power per square meter collected by a solar collector on the ground will always be less than what you found in part b. d. Suppose you want to put a solar collector on your roof. If you want to optimize the amount of power you can collect, how…arrow_forward
- How can we know that the sun will “die” in about 5 billion years? Choose the correct answer. A. We can see the evolution and death in the spectra B. We can see the entire process as it plays out in a star C. We look at thousands of stars like the sun and can see them in all stages of developmentarrow_forward"51 Pegasi" is the name of the first normal star (besides the Sun) around which a planet was discovered. It is in the constellation Pegasus the horse. Its parallax is measured to be 0.064 arcsec. a. What is its distance from us? b. The apparent brightness is 1.79 × 10-10 J/(s·m2 ). What is the luminosity? How does that compare with that of the Sun? Look up the temperature: how doarrow_forward. The spectrum of Star A peaks at 700 nm. The spectrum of Star B peaks at 470 nm. We know nothing about what stage of stellar evolution either of these stars are in. Which of the following are true? A. Star A has a higher luminosity than Star B. B. Star B has a higher luminosity than Star A. C. Star A is cooler than Star B. D. Not enough information to comment on their luminosities. E. B and C F. C and Darrow_forward
- Tutorial Star A has a temperature of 6,000 K. How much energy per second (in J/s/m²) does it radiate onto a square meter of its surface? If the temperature of Star A decreases by a factor of 2, the energy will decrease by a factor of Star B has a temperature that is 5 times higher than Star A. How much more energy per second (compared to Star A) does it radiate onto a square meter of its surface? Part 1 of 4 The energy of a star is related to its temperature by E = OTA where o = 5.67 x 10-8 J/s/m²/K4. Part 2 of 4 To determine how much energy Star A is radiating, we just plug in the temperature to solve for EA. EA J/s/m²arrow_forwardTutorial Star A has a temperature of 5,000 K. How much energy per second (in J/s/m2) does it radiate from a square meter of its surface? If the temperature of Star A decreases by a factor of 2, the energy will decrease by a factor of Star B has a temperature that is 5 times higher than Star A. How much more energy per second (compared to Star A) does it radiate from a square meter of its surface? Part 1 of 4 The energy of a star is related to its temperature by E = GT4 where σ = 5.67 x 10-8 J/s/m2/K4. Part 2 of 4 To determine how much energy Star A is radiating, we just plug in the temperature to solve for EA. EA = J/s/m² Submit Skip (you cannot come back)arrow_forwardTutorial Star A has a temperature of 5,000 K and Star B has a temperature of 6,000 K. At what wavelengths (in nm) will each of these star's intensity be at its maximum? If the temperatures of the stars increase, the wavelength of maximum intensity. What is the temperature (in K) of a star that appears most intense at a wavelength of 829 nm? Part 1 of 4 Wien's Law tells us how the temperature of a star determines the wavelength of maximum intensity or at what wavelength the star appears brightest. 2.90 x 106 TK If the temperature is in kelvin (K) then A is in nanometers (nm). Anm ^A = AB = = Part 2 of 4 To determine the wavelengths of maximum intensity for the two stars: 2.90 x 106 2.90 x 106 K nm nmarrow_forward
- 1. The Sun radiates energy like a black body with temperature 5800 K. Use the Stefan-Boltzmann Law to calculate the Sun's Luminosity (which is the Sun's Surface Area times the Flux radiated per unit surface area. Use the following parameters: Sun's Radius = R = 6.96 x 1010 cm Stefan-Boltzmann Const = s = 5.67 x 10-5 ergs/cm2 K4 sSun's Temperature = T = 5800 K Formula for Luminosity: L = 4pR2 sT 4 What is the Sun's Luminosity? __________ ergs/sarrow_forwardThe spectrum of a typical star shows absorption lines at different wavelengths than their laboratory values. If the observed wavelength is less than its laboratory value of 656.3 nm, one can conclude that... A. The separation between Earth and the star is decreasing. B. The separation between Earth and the star is increasing. C. The separation between Earth and the star is unchanging D. No conclusion is possible.arrow_forwardThe spectrum of a typical star shows absorption lines at different wavelengths than their laboratory values. If the observed wavelength is greater than its laboratory value of 656.3 nm, one can conclude that... A. The separation between Earth and the star is decreasing. B. The separation between Earth and the star is increasing. C. The separation between Earth and the star is unchanging D. No conclusion is possible.arrow_forward
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