Loose Leaf For Explorations: Introduction To Astronomy
9th Edition
ISBN: 9781260432145
Author: Thomas T Arny, Stephen E Schneider Professor
Publisher: McGraw-Hill Education
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Chapter 16, Problem 7TY
To determine
The correct option for the Milky Way that has spiral arms.
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A galaxy's rotation curve is a measure of the orbital speed of stars as a function of distance
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dark matter exists. Let's work out why!
Assuming that each star in a given galaxy has a circular orbit, we know that the accelera-
tion due to gravity felt by each star is due to the mass enclosed within its orbital radius r and
equal to v?/r. Here, ve is the circular orbit velocity of the star. (a) Show that the expected
relationship between ve and r due to the stellar halo (p(r) xr-3.5) does not produce a flat
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tation curve and must therefore be the general profile that dark matter follows in our galaxy.
An important part of the lifecycle of galaxies like the Milky Way is the self regulation of formation of future generations of stars. Which statement best describes this process?
A) Massive stars explode as Supernovae, heating nearby gas which then can't form stars, and even forcing the gas out of the galaxy in asuperbubble.
B) Low mass stars like our Sun explode as Supernovae, heating nearby gas which then can't form stars, and even forcing the gas out the galaxy in asuperbubble.
C) Stars fuse new elements in their cores which mix with nearby gas clouds, preventing the collapse of the clouds and hence stopping new starformation.
D) The stars lock up material in their cores (like White Dwarf and Neutron Stars) meaning they can act as gravitational seeds for future starformation.
Globular clusters revolve around the Galaxy in highly elliptical orbits. Where would you expect the clusters to spend most of their time? (Think of Kepler’s laws.) At any given time, would you expect most globular clusters to be moving at high or low speeds with respect to the center of the Galaxy? Why? (If you would like to learn more about globular clusters, read Section 22.2 of the book, though it is not necessary to answer this question)
Chapter 16 Solutions
Loose Leaf For Explorations: Introduction To Astronomy
Ch. 16 - Prob. 1QFRCh. 16 - How do we know our Galaxy is a flat disk?Ch. 16 - Prob. 3QFRCh. 16 - Prob. 4QFRCh. 16 - Prob. 5QFRCh. 16 - Prob. 6QFRCh. 16 - Prob. 7QFRCh. 16 - Prob. 8QFRCh. 16 - Prob. 9QFRCh. 16 - Prob. 10QFR
Ch. 16 - Prob. 11QFRCh. 16 - Prob. 12QFRCh. 16 - Prob. 13QFRCh. 16 - Prob. 14QFRCh. 16 - Prob. 15QFRCh. 16 - Prob. 16QFRCh. 16 - Prob. 17QFRCh. 16 - Prob. 18QFRCh. 16 - Prob. 19QFRCh. 16 - Prob. 20QFRCh. 16 - Prob. 21QFRCh. 16 - Prob. 1TQCh. 16 - Prob. 2TQCh. 16 - Prob. 3TQCh. 16 - Prob. 4TQCh. 16 - Prob. 5TQCh. 16 - Prob. 7TQCh. 16 - Prob. 8TQCh. 16 - Prob. 9TQCh. 16 - Prob. 10TQCh. 16 - Prob. 1PCh. 16 - Prob. 2PCh. 16 - Prob. 3PCh. 16 - Prob. 4PCh. 16 - Prob. 5PCh. 16 - Prob. 6PCh. 16 - Prob. 7PCh. 16 - Prob. 8PCh. 16 - Prob. 9PCh. 16 - Prob. 1TYCh. 16 - Prob. 2TYCh. 16 - Prob. 3TYCh. 16 - Prob. 4TYCh. 16 - Prob. 5TYCh. 16 - Prob. 6TYCh. 16 - Prob. 7TYCh. 16 - Prob. 8TYCh. 16 - Prob. 9TYCh. 16 - Prob. 10TY
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- Consider the following five kinds of objects: open cluster, giant molecular cloud, globular cluster, group of O and B stars, and planetary nebulae. A. Which occur only in spiral arms? B. Which occur only in the parts of the Galaxy other than the spiral arms? C. Which are thought to be very young? D. Which are thought to be very old? E. Which have the hottest stars?arrow_forwardA given star orbits the center of its galaxy at an average speed of v_star, at a distance of r_star from the center. The galaxy has 2 spiral arms, and the arms themselves orbit slower than the star -- at the same radius, they orbit at a speed of v_arm (in the same direction as the star). The galaxy's age is t_gal. In the history of this galaxy, how many times did this star cross through a spiral arm? Values: v_star = 200 km/s, r_star = 9 kpc, v_arms = 46 km/s, t_gal = 4 Gyrarrow_forwardThe very first “image" of a black hole, at the centre of galaxy M87, was recently taken by the Event Horizon Telescope (EHT). More accurately, EHT imaged radio emission from the disc of gas that orbits the black hole with a lack of emission from the centre being attributed to the black hole. This image was only possible because EHT is not a single radio telescope, but is in fact a network of telescopes from around the world that take advantage of something known as interferometry. Interferometry is a method for combining the light from multiple telescopes, which results in an image that could have been taken by a telescope that has a diameter equal to the distance between the telescopes referred to as the "“baseline"-rather than the size of each individual telescope. EHT in particular combines observations from several Very Long Baseline Interferometry (VLBI) stations in order to achieve a high angular resolution. (a) Given that the "baseline" of EHT is effectively the diameter of the…arrow_forward
- The very first "image" of a black hole, at the centre of galaxy M87, was recently taken by the Event Horizon Telescope (EHT). More accurately, EHT imaged radio emission from the disc of gas that orbits the black hole with a lack of emission from the centre being attributed to the black hole. This image was only possible because EHT is not a single radio telescope, but is in fact a network of telescopes from around the world that take advantage of something known as interferometry. Interferometry is a method for combining the light from multiple telescopes, which results in an image that could have been taken by a telescope that has a diameter equal to the distance between the telescopes-referred to as the “baseline"-rather than the size of each individual telescope. EHT in particular combines observations from several Very Long Baseline Interferometry (VLBI) stations in order to achieve a high angular resolution. (a) Given that the "baseline" of EHT is effectively the diameter of the…arrow_forwardFigure 2 shows the "rotation curve" of NGC 2742. It plots the “radial velocity (V)" (how fast material is moving either toward or away from us) that is measured for objects at different distances (R = radius") from the center of the galaxy. The center of the galaxy is at 0 kpc (kiloparsecs) with a speed of 9 km/sec away from us. (These velocities have been corrected for the observed tilt of the galaxy and represent true orbital velocities of the stars and gas.) 200 100 U4779 -100 As you can see, one side of the galaxy is moving with a negative velocity (spinning toward us), while the other side has a positive velocity (spinning away from us). Using Newton's gravity equation, we will be able to determine the gravitational mass of the entire galaxy and how the mass varies versus distance from the galaxy's center. -200 -8 8 -4 Radius (kpc) Read the following text carefully and follow the instructions: Select five radii spaced evenly from 0-10 kpc across the galaxy. Your selections should…arrow_forwardIndicate whether the following statements are true or false. (Select T-True, F-False. If the first is T and the rest F, enter TFFFFF). A) If we find an O type star in our galaxy, it must be in the disk. B) The nearest large spiral Galaxy, similar in size to the Milky Way, is the Andromeda Galaxy (M31). It is located about 2 million light years from Earth. C) The disk of the Milky Way galaxy is about 100,000 light years in diameter. D) On very large scales, matter in the Universe is distributed in clumps and voids. E) Distances to most stars in the Milky Way are measured by parallax. F) RR Lyrae and Cepheid variable stars are used to measure the distance to nearby galaxies.arrow_forward
- The 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_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 determine the mass in the Milky Way that lies interior to 50 kpc. Express your answer in units of the Solar mass. 250 km s-1. Using Kepler's 3rd Law,arrow_forwardAmong the globular clusters orbiting a distant galaxy, one is moving at 534 km/s and is located 14 kpc from the center of the galaxy. Assuming the globular cluster is located outside most of the mass of the galaxy, what is the mass of the galaxy? Convert your answer to solar masses. (Hint: Use the formula for circular velocity, Vc = GM r ; make sure you convert relevant quantities to units of meters, kilograms, and seconds. Note: 1 pc = 3.1 ✕ 1016 m.)arrow_forward
- You observe a star orbiting the massive object at the galactic center at a speed of 1090 km/s in a circular orbit with a radius of 18 light-days. Calculate the mass of the object the star is orbiting. Enter in solar masses Hint: The orbital velocity equation is v=sqrt(G M / R). Also note that the orbital radius is in light DAYS.arrow_forwardThe figure below shows the spectra of two galaxies A and B. Please can i get help with this questions below: 1. Which of these galaxies has ongoing star formation? How can you tell?2. One of these galaxies has Hubble type E3 while the other is SBb. Which is which? What does the 3 inE3 tell you about the galaxy? What does the SB in SBb tell you about the galaxy?3. What effects would dust have on the two spectra?4. Which galaxy would you expect to have more far-infrared emission? Explarrow_forwardWhy does star formation occur primarily in the disk of the Galaxy?arrow_forward
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