EBK LOOSE-LEAF VERSION OF UNIVERSE
11th Edition
ISBN: 9781319227975
Author: KAUFMANN
Publisher: VST
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Chapter 20, Problem 4Q
To determine
The way in which horizontal-branch stars can be differentiated from main-sequence stars if some main-sequence stars of the galaxy have similar luminosity and surface temperature as the horizontal-branch stars in the globular cluster M55.
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Students have asked these similar questions
How are giant molecular clouds (GMCs), the loci of most star formation, themselves formed out of diffuse interstellar gas?
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The figure below shows the spectra of two galaxies A and B.
If you want to find a sizeable collection of Population Il stars in the Milky Way Galaxy, where
would be a good place to look?
A. near the Sun
B. in a globular cluster high above the Galaxy's disk
C. in the Orion Spur
D.on the outer surface of giant molecular clouds
E. in an open cluster, especially one with a lot of dust in and around it
Chapter 20 Solutions
EBK LOOSE-LEAF VERSION OF UNIVERSE
Ch. 20 - Prob. 1CCCh. 20 - Prob. 2CCCh. 20 - Prob. 3CCCh. 20 - Prob. 4CCCh. 20 - Prob. 5CCCh. 20 - Prob. 6CCCh. 20 - Prob. 7CCCh. 20 - Prob. 8CCCh. 20 - Prob. 9CCCh. 20 - Prob. 10CC
Ch. 20 - Prob. 11CCCh. 20 - Prob. 12CCCh. 20 - Prob. 13CCCh. 20 - Prob. 14CCCh. 20 - Prob. 15CCCh. 20 - Prob. 16CCCh. 20 - Prob. 17CCCh. 20 - Prob. 18CCCh. 20 - Prob. 1QCh. 20 - Prob. 2QCh. 20 - Prob. 3QCh. 20 - Prob. 4QCh. 20 - Prob. 5QCh. 20 - Prob. 6QCh. 20 - Prob. 7QCh. 20 - Prob. 8QCh. 20 - Prob. 9QCh. 20 - Prob. 10QCh. 20 - Prob. 11QCh. 20 - Prob. 12QCh. 20 - Prob. 13QCh. 20 - Prob. 14QCh. 20 - Prob. 15QCh. 20 - Prob. 16QCh. 20 - Prob. 17QCh. 20 - Prob. 18QCh. 20 - Prob. 19QCh. 20 - Prob. 20QCh. 20 - Prob. 21QCh. 20 - Prob. 22QCh. 20 - Prob. 23QCh. 20 - Prob. 24QCh. 20 - Prob. 25QCh. 20 - Prob. 26QCh. 20 - Prob. 27QCh. 20 - Prob. 28QCh. 20 - Prob. 29QCh. 20 - Prob. 30QCh. 20 - Prob. 31QCh. 20 - Prob. 32QCh. 20 - Prob. 33QCh. 20 - Prob. 34QCh. 20 - Prob. 35QCh. 20 - Prob. 36QCh. 20 - Prob. 37QCh. 20 - Prob. 38QCh. 20 - Prob. 39QCh. 20 - Prob. 40QCh. 20 - Prob. 41QCh. 20 - Prob. 42QCh. 20 - Prob. 43QCh. 20 - Prob. 44QCh. 20 - Prob. 45QCh. 20 - Prob. 46QCh. 20 - Prob. 47QCh. 20 - Prob. 48QCh. 20 - Prob. 49QCh. 20 - Prob. 50QCh. 20 - Prob. 51QCh. 20 - Prob. 52QCh. 20 - Prob. 53QCh. 20 - Prob. 54QCh. 20 - Prob. 55QCh. 20 - Prob. 56QCh. 20 - Prob. 57QCh. 20 - Prob. 58QCh. 20 - Prob. 59QCh. 20 - Prob. 60QCh. 20 - Prob. 61QCh. 20 - Prob. 62QCh. 20 - Prob. 63QCh. 20 - Prob. 64QCh. 20 - Prob. 65QCh. 20 - Prob. 66QCh. 20 - Prob. 67QCh. 20 - Prob. 68QCh. 20 - Prob. 69QCh. 20 - Prob. 70QCh. 20 - Prob. 71QCh. 20 - Prob. 72QCh. 20 - Prob. 73QCh. 20 - Prob. 74QCh. 20 - Prob. 75Q
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- If the Sun were a member of the cluster NGC 2264, would it be on the main sequence yet? Why or why not?arrow_forwardA molecular cloud is about 1000 times denser than the average of the interstellar medium. Let’s compare this difference in densities to something more familiar. Air has a density of about 1 kg/m3, so something 1000 times denser than air would have a density of about 1000 kg/m3. How does this compare to the typical density of water? Of granite? (You can find figures for these densities on the internet.) Is the density difference between a molecular cloud and the interstellar medium larger or smaller than the density difference between air and water or granite?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
- You 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_forwardThe 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_forwardYou can estimate the age of the planetary nebula in image (c) in Figure 22.18. The diameter of the nebula is 600 times the diameter of our own solar system, or about 0.8 light-year. The gas is expanding away from the star at a rate of about 25 mi/s. Considering that distance=velocitytime , calculate how long ago the gas left the star if its speed has been constant the whole time. Make sure you use consistent units for time, speed, and distance. Figure 22.18 Gallery of Planetary Nebulae. This series of beautiful images depicting some intriguing planetary nebulae highlights the capabilities of the Hubble Space Telescope. (a) Perhaps the best known planetary nebula is the Ring Nebula (M57), located about 2000 lightyears away in the constellation of Lyra. The ring is about 1 light-year in diameter, and the central star has a temperature of about 120,000 °C. Careful study of this image has shown scientists that, instead of looking at a spherical shell around this dying star, we may be looking down the barrel of a tube or cone. The blue region shows emission from very hot helium, which is located very close to the star; the red region isolates emission from ionized nitrogen, which is radiated by the coolest gas farthest from the star; and the green region represents oxygen emission, which is produced at intermediate temperatures and is at an intermediate distance from the star. (b) This planetary nebula, M2-9, is an example of a butterfly nebula. The central star (which is part of a binary system) has ejected mass preferentially in two opposite directions. In other images, a disk, perpendicular to the two long streams of gas, can be seen around the two stars in the middle. The stellar outburst that resulted in the expulsion of matter occurred about 1200 years ago. Neutral oxygen is shown in red, once-ionized nitrogen in green, and twice-ionized oxygen in blue. The planetary nebula is about 2100 light-years away in the constellation of Ophiuchus. (c) In this image of the planetary nebula NGC 6751, the blue regions mark the hottest gas, which forms a ring around the central star. The orange and red regions show the locations of cooler gas. The origin of these cool streamers is not known, but their shapes indicate that they are affected by radiation and stellar winds from the hot star at the center. The temperature of the star is about 140,000 °C. The diameter of the nebula is about 600 times larger than the diameter of our solar system. The nebula is about 6500 light-years away in the constellation of Aquila. (d) This image of the planetary nebula NGC 7027 shows several stages of mass loss. The faint blue concentric shells surrounding the central region identify the mass that was shed slowly from the surface of the star when it became a red giant. Somewhat later, the remaining outer layers were ejected but not in a spherically symmetric way. The dense clouds formed by this late ejection produce the bright inner regions. The hot central star can be seen faintly near the center of the nebulosity. NGC 7027 is about 3000 light-years away in the direction of the constellation of Cygnus. (credit a: modification of work by NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; credit b: modification of work by Bruce Balick (University of Washington), Vincent Icke (Leiden University, The Netherlands), Garrelt Mellema (Stockholm University), and NASA; credit c: modification of work by NASA, The Hubble Heritage Team (STScI/AURA); credit d: modification of work by H. Bond (STScI) and NASA)arrow_forward
- Using the information provided in Table 18.1, what is the average stellar density in our part of the Galaxy? Use only the true stars (types OM) and assume a spherical distribution with radius of 26 light-years. Stars within 21 Light-Years of the Sunarrow_forwardH II regions can exist only if there is a nearby star hot enough to ionize hydrogen. Hydrogen is ionized only by radiation with wavelengths shorter than 91.2 nm. What is the temperature of a star that emits its maximum energy at 91.2 nm? (Use Wien’s law from Radiation and Spectra.) Based on this result, what are the spectral types of those stars likely to provide enough energy to produce H II regions?arrow_forwardFrom the comments in the text about which kinds of stars produce emission nebulae and which kinds are associated with reflection nebulae, what can you say about the temperatures of the stars that produce NGC 1999 (Figure 20.13)? Figure 20.13 Pleiades Star Cluster. The bluish light surrounding the stars in this image is an example of a reflection nebula. Like fog around a street lamp, a reflection nebula shines only because the dust within it scatters light from a nearby bright source. The Pleiades cluster is currently passing through an interstellar cloud that contains dust grains, which scatter the light from the hot blue stars in the cluster. The Pleiades cluster is about 400 light-years from the Sun. (credit: NASA, ESA and AURA/Caltech)arrow_forward
- Suppose the Sagittarius dwarf galaxy merges completely with the Milky Way and adds 150,000 stars to it. Estimate the percentage change in the mass of the Milky Way. Will this be enough mass to affect the orbit of the Sun around the galactic center? Assume that all of the Sagittarius galaxy’s stars end up in the nuclear bulge of the Milky Way Galaxy and explain your answer.arrow_forwardWould you expect to observe every supernova in our own Galaxy? Why or why not?arrow_forwardThe best parallaxes obtained with Hipparcos have an accuracy of 0.001 arcsec. If you want to measure the distance to a star with an accuracy of 10%, its parallax must be 10 times larger than the typical error. How far away can you obtain a distance that is accurate to 10% with Hipparcos data? The disk of our Galaxy is 100,000 light-years in diameter. What fraction of the diameter of the Galaxy’s disk is the distance for which we can measure accurate parallaxes?arrow_forward
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