Universe: Stars And Galaxies
6th Edition
ISBN: 9781319115098
Author: Roger Freedman, Robert Geller, William J. Kaufmann
Publisher: W. H. Freeman
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Chapter 22, Problem 11Q
To determine
The reason for the interstellar hydrogen atoms to emit only radio waves of wavelength
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(a) Rank the following components of the interstellar medium in order of the wavelengths at which they are observed, longest wavelength first: clouds of neutral hydrogen, coronal gas, interstellar dust, nebulae. Longest to Shortest?
(b) Rank the same material in order of decreasing temperature from hottest to coolest. Hottest to Coolest?
What factors resist the contraction of a cloud of interstellar matter?
Phyisics:
Extinction dims starlight by about 1 magnitude per 1000 pc. What fraction of photons survives a trip of 1000 pc?
The expanding bubble of hot gas inflated by the cluster of new stars in its center, shown in Figure 9-7a, has a diameter of about 70 ly. If the bubble is 170,000 ly from Earth, what is the observed diameter of the bubble in arcseconds?
Chapter 22 Solutions
Universe: Stars And Galaxies
Ch. 22 - Prob. 1QCh. 22 - Prob. 2QCh. 22 - Prob. 3QCh. 22 - Prob. 4QCh. 22 - Prob. 5QCh. 22 - Prob. 6QCh. 22 - Prob. 7QCh. 22 - Prob. 8QCh. 22 - Prob. 9QCh. 22 - Prob. 10Q
Ch. 22 - Prob. 11QCh. 22 - Prob. 12QCh. 22 - Prob. 13QCh. 22 - Prob. 14QCh. 22 - Prob. 15QCh. 22 - Prob. 16QCh. 22 - Prob. 17QCh. 22 - Prob. 18QCh. 22 - Prob. 19QCh. 22 - Prob. 20QCh. 22 - Prob. 21QCh. 22 - Prob. 22QCh. 22 - Prob. 23QCh. 22 - Prob. 24QCh. 22 - Prob. 25QCh. 22 - Prob. 26QCh. 22 - Prob. 27QCh. 22 - Prob. 28QCh. 22 - Prob. 29QCh. 22 - Prob. 30QCh. 22 - Prob. 31QCh. 22 - Prob. 32QCh. 22 - Prob. 33QCh. 22 - Prob. 34QCh. 22 - Prob. 35QCh. 22 - Prob. 36QCh. 22 - Prob. 37QCh. 22 - Prob. 38QCh. 22 - Prob. 39QCh. 22 - Prob. 40QCh. 22 - Prob. 41QCh. 22 - Prob. 42QCh. 22 - Prob. 43QCh. 22 - Prob. 44QCh. 22 - Prob. 45QCh. 22 - Prob. 46QCh. 22 - Prob. 47QCh. 22 - Prob. 48QCh. 22 - Prob. 49QCh. 22 - Prob. 50Q
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- The mass of the interstellar medium is determined by a balance between sources (which add mass) and sinks (which remove it). Make a table listing the major sources and sinks, and briefly explain each one.arrow_forwardWhere does interstellar dust come from? How does it form?arrow_forwardHow would the density inside a cold cloud (T=10K) compare with the density of the ultra-hot interstellar gas (T=106K) if they were in pressure equilibrium? (It takes a large cloud to be able to shield its interior from heating so that it can be at such a low temperature.) (Hint: In pressure equilibrium, the two regions must have nT equal, where n is the number of particles per unit volume and T is the temperature.) Which region do you think is more suitable for the creation of new stars? Why?arrow_forward
- Suppose that you gathered a ball of interstellar gas that was equal to the size of Earth (a radius of about 6000 km). If this gas has a density of 1 hydrogen atom per cm3, typical of the interstellar medium, how would its mass compare to the mass of a bowling ball (5 or 6 kg)? How about if it had the typical density of the Local Bubble, about 0.01 atoms per cm3? The volume of a sphere is V=(4/3)R3 .arrow_forwardConsider a grain of sand that contains 1 mg of oxygen (a typical amount for a medium-sized sand grain, since sand is mostly SiO2). How many oxygen atoms does the grain contain? What is the radius of the sphere you would have to spread them out over if you wanted them to have the same density as the interstellar medium, about 1 atom per cm3? You can look up the mass of an oxygen atom.arrow_forwardDescribe the characteristics of the various kinds of interstellar gas (HII regions, neutral hydrogen clouds, ultra-hot gas clouds, and molecular clouds).arrow_forward
- Describe how the 21-cm line of hydrogen is formed. Why is this line such an important tool for understanding the interstellar medium?arrow_forwardHow are giant molecular clouds (GMCs), the loci of most star formation, themselves formed out of diffuse interstellar gas? What processes determine the distribution of physical conditions within star-forming regions, and why does star formation occur in only a small fraction of the available gas? How is the rate at which stars form determined by the properties of the natal GMC or, on a larger scale, of the interstellar medium (ISM) in a galaxy? What determines the mass distribution of forming stars, the initial mass function (IMF)? Most stars form in clusters (Lada & Lada 2003); how do stars form in such a dense environment and in the presence of enormous radiative and mechanical feedback from other YSOs?arrow_forwardWhat evidence can you cite that the interstellar medium contains both gas and dust? (Select all that apply.) (1)The dust of the interstellar medium can be detected from the emission lines of elements heavier than iron. (2)The dust of the interstellar medium can be detected by the extinction of light from distant stars. (3)The dust of the interstellar medium can be detected by the scattering of blue light from distant or embedded objects. (4)The gas of the interstellar medium can be detected from the radiation of ultraviolet photons. (5)The gas of the interstellar medium can be detected from the radiation of photons of wavelength 21 cm. (6)The gas of the interstellar medium can be detected from the absorption lines present in the light from distant stars, which must be caused by a medium of a density and temperature other than that of the stars emitting the light.arrow_forward
- If the hottest star in the Carina Nebula has a surface temperature of 51,000 K, at what wavelength (in nm) does it radiate the most energy? Hint: Use Wien's law: ?max = 2.90 ✕ 106 nm · K T How does that compare with 91.2 nm, the wavelength of photons with just enough energy to ionize hydrogen? -The wavelength calculated above is shorter than 91.2 nm. Photons at this calculated wavelength will have more than enough energy to ionize hydrogen. -The wavelength calculated above is longer than 91.2 nm. Photons at this calculated wavelength will have more than enough energy to ionize hydrogen. -The wavelength calculated above is shorter than 91.2 nm. Photons at this calculated wavelength will not have enough energy to ionize hydrogen. -The wavelength calculated above is longer than 91.2 nm. Photons at this calculated wavelength will not have enough energy to ionize hydrogen.arrow_forwardExplain why the sky is blue and how that relates to reflection nebulae.arrow_forwardAt the average density of a star-forming molecular cloud, about 900 atoms per cm3, determine how large a sphere you would need to encompass mass equal to that of the Sun? Enter the radius of this sphere in light-years. (HINTS: 900 atoms per cm3 corresponds to a density of 1.51×10-18kg/m^3; the mass of the Sun is 2×1030kg) (The volume of a sphere is 4/3 * π * R3) (my previous answer of 6.812 X 1015 was incorrect)arrow_forward
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