Understanding Our Universe
3rd Edition
ISBN: 9780393614428
Author: PALEN, Stacy, Kay, Laura, Blumenthal, George (george Ray)
Publisher: W.w. Norton & Company,
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Chapter 15, Problem 9QAP
To determine
Reason why MACHOs are found in halo.
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Absorption 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.
Absorption 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.
Why are interstellar lines so narrow?
Chapter 15 Solutions
Understanding Our Universe
Ch. 15.1 - Prob. 15.1CYUCh. 15.2 - Prob. 15.2CYUCh. 15.3 - Prob. 15.3CYUCh. 15.4 - Prob. 15.4CYUCh. 15 - Prob. 1QAPCh. 15 - Prob. 2QAPCh. 15 - Prob. 3QAPCh. 15 - Prob. 4QAPCh. 15 - Prob. 5QAPCh. 15 - Prob. 6QAP
Ch. 15 - Prob. 7QAPCh. 15 - Prob. 8QAPCh. 15 - Prob. 9QAPCh. 15 - Prob. 10QAPCh. 15 - Prob. 11QAPCh. 15 - Prob. 12QAPCh. 15 - Prob. 13QAPCh. 15 - Prob. 14QAPCh. 15 - Prob. 15QAPCh. 15 - Prob. 16QAPCh. 15 - Prob. 17QAPCh. 15 - Prob. 18QAPCh. 15 - Prob. 19QAPCh. 15 - Prob. 20QAPCh. 15 - Prob. 21QAPCh. 15 - Prob. 22QAPCh. 15 - Prob. 23QAPCh. 15 - Prob. 24QAPCh. 15 - Prob. 25QAPCh. 15 - Prob. 26QAPCh. 15 - Prob. 27QAPCh. 15 - Prob. 28QAPCh. 15 - Prob. 29QAPCh. 15 - Prob. 30QAPCh. 15 - Prob. 31QAPCh. 15 - Prob. 32QAPCh. 15 - Prob. 33QAPCh. 15 - Prob. 34QAPCh. 15 - Prob. 35QAPCh. 15 - Prob. 36QAPCh. 15 - Prob. 37QAPCh. 15 - Prob. 38QAPCh. 15 - Prob. 39QAPCh. 15 - Prob. 40QAPCh. 15 - Prob. 41QAPCh. 15 - Prob. 42QAPCh. 15 - Prob. 43QAPCh. 15 - Prob. 44QAPCh. 15 - Prob. 45QAP
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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_forwardThe Tully-Fischer method relies on being able to relate the mass of a galaxy to its rotation velocity. Stars in the outer-most regions of the Milky Way galaxy, located at a distance of 50 kpc from the galactic centre, are observed to orbit at a speed vrot = 250 km s−1. Using Kepler’s 3rd Law, determine the mass in the Milky Way that lies interior to 50 kpc. Express your answer in units of the Solar mass.arrow_forwardIf 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 itarrow_forward
- A 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_forwardSuppose 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_forwardAssume that dark matter is uniformly distributed throughout the Milky Way, not just in the outer halo but also throughout the bulge and in the disk, where the solar system lives. How much dark matter would you expect there to be inside the solar system? Would you expect that to be easily detectable? Hint: For the radius of the Milky Way’s dark matter halo, use R=300,000 light-years; for the solar system’s radius, use 100 AU; and start by calculating the ratio of the two volumes.arrow_forward
- Our galaxy is suspected to be surrounded by a galactic corona because the disk of the galaxy a. rotates faster than expected in its outer region. b. rotates more slowly than expected in its outer region. c. rotates faster than expected in its inner region. d. rotates more slowly than expected in its inner region. e. is much flatter than expectedarrow_forwardRadio maps of our galaxy show spiral arms because a. the arms have larger Doppler shifts. b. the gas in the spiral arms is very hot. c. the dust in spiral arms is denser. d. the gas in spiral arms is denser. e. the stars in the spiral arms emit most of their energy at radio wavelengths.arrow_forwardThe spectra of the cores of Seyfert galaxies contain emission lines of highly ionized atoms that are a. split from the strong electric fields. b. blueshifted. c. split from the strong magnetic fields. d. broadened. e. all of the above.arrow_forward
- Some interstellar Properties. Use excel calculator to fill in the missing figures. 1 ly = 365 × 24 × 60 × 60 × 300, 000km/s = 9.46 × 10^12 kmarrow_forwardDisk population stars have I. circular orbits in the plane of the galaxy II. randomly tipped, elliptical orbits III. old stars with low metal content IV. young stars with heavy metal content a. I and II b. I and III c. II and III d. II and IV e. I and IVarrow_forwardWhat is the name for the spherical cloud of thinly scattered stars and globular clusters that contain only about 2 percent as many stars as the disk of the galaxy and has very little gas and dust? a. the core b. the nuclear bulge c. the spiral arms d. the halo e. none of thesearrow_forward
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