Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 20, Problem 18E
Describe the spectrum of each of the following:
A. starlight reflected by dust,
B. a star behind invisible interstellar gas, and
C. an emission nebula.
Expert Solution & Answer
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Students have asked these similar questions
Why don’t we see hydrogen Balmer lines in the spectra of stars with temperatures of 3,200 K?
a.
There is no hydrogen in stars this cool.
b.
The stars are hot enough that most of the hydrogen is ionized and the atoms cannot absorb energy.
c.
These stars are so cool that nearly all of the hydrogen atoms are in the ground state.
d.
Stars of this temperature are too cool to produce an absorption spectrum.
e.
Stars of this temperature are too hot to produce an absorption spectrum.
. 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 D
The 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.
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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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- Why evidence can you cite that the interstellar medium contains both gas and dust?arrow_forwardSpectral 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_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_forward
- Suppose a spectral line from an object in space was shifted from 5007.0 to 5100.0 Angstroms. What can we tell about this object? A) It is a star. B) It is very cold. C) It is blueshifted, hence coming towards us. D) Its radial velocity is positive, meaning it is moving away from us. E) It is a planet in a distant galaxy. F) It is an exoplanet.arrow_forwardAbsorption lines produced when starlight travels through the interstellar medium indicate that some components of the interstellar medium are cold and of a very low density because a. the lines are blueshifted. b. the lines are redshifted. c. the lines are extremely broad. d. the lines are extremely narrow. e. the lines are much darker than the stellar lines.arrow_forwardAbsorption lines produced by interstellar gas a. are wider than the lines from stars because the gas is hotter than most stars. b. are more narrow than the lines from stars because the gas has a lower pressure than stars. c. indicate that the interstellar medium contains dust. d. indicate that the interstellar medium is expanding away from the sun. e. indicate nothing; none of the above statements are true.arrow_forward
- 57. 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_forward4. Suppose we observe a binary star system in which one star is much more massive than the other and both are on the main sequence. We measure that the smaller star orbits the larger at a distance of 10¹3 m with a speed of 10 m/s. a. What is the mass of the larger star? b. Which star has a higher luminosity? c. Which has a larger radius? d. Which is hotter?arrow_forward12. A star with spectral type MO has a surface temperature of 3750 K and a radius of 0.63 Rsun: How many times more luminous is this star than the Sun? (if it is less luminous enter a number less than one) Answer: Submit All Answers Last Answer: 0.0923 Incorrect, tries 1/5. Hint: Use the Luminosity equation, which says that L is proportional to R^2 T^4. If you keep these as ratios compared to the sun, your L will also come out as a ratio compared to the Sun. This star has a mass of 0.4 Msun- Using the simple approximation that we made in class, what is the main sequence lifetime of this star? You may assume that the lifetime of the sun is 1010 yr. Answer: Submit All Answers Compare this to the lifetime of a MO star listed in Table 22.1 (computed using a more sophisticated approach). Is the value you calculated in the previous problem longer or shorter than what is reported in the table? (L for longer, S for shorter) (You only get one try at this problem.) Answer: Submit All Answersarrow_forward
- A group of four stars, all the same size, have the four different surface temperatures given below. Which of these stars emits the most red light?A. 3000 K B. 4000 K C. 5000 K D. 6000 Karrow_forwardIf the stars Betelgeuse and Rigel each have the same luminosity, but the temperature of Betelgeuse is lower than Rigel, which star has the greater surface area? O A. Betelgeuse B. Rigel O C. They are the same size. OD. There is insufficient information to answer this question.arrow_forward1. 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_forward
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