21ST CENT.ASTRONOMY(LL)W/CODE WKBK PKG.
6th Edition
ISBN: 9780393874921
Author: PALEN
Publisher: Norton, W. W. & Company, Inc.
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Question
Chapter 20, Problem 35QP
(a)
To determine
The time taken for globular cluster to complete one trip around galactic centre.
(b)
To determine
The number of orbits made by globular cluster.
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n(r) = 1ge
where r represents the distance from the centre of the Galaxy, Ro is
the distance of the Sun from the centre of the Galaxy, Ra is the typical
size of disk and no is the stellar density of disk at the position of the
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center of the Galaxy within a small field of view. We take a particular
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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
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,
Figure 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…
Chapter 20 Solutions
21ST CENT.ASTRONOMY(LL)W/CODE WKBK PKG.
Ch. 20.1 - Prob. 20.1CYUCh. 20.2 - Prob. 20.2CYUCh. 20.3 - Prob. 20.3CYUCh. 20.4 - Prob. 20.4CYUCh. 20 - Prob. 1QPCh. 20 - Prob. 2QPCh. 20 - Prob. 3QPCh. 20 - Prob. 4QPCh. 20 - Prob. 5QPCh. 20 - Prob. 6QP
Ch. 20 - Prob. 7QPCh. 20 - Prob. 8QPCh. 20 - Prob. 9QPCh. 20 - Prob. 10QPCh. 20 - Prob. 11QPCh. 20 - Prob. 12QPCh. 20 - Prob. 13QPCh. 20 - Prob. 14QPCh. 20 - Prob. 15QPCh. 20 - Prob. 16QPCh. 20 - Prob. 17QPCh. 20 - Prob. 18QPCh. 20 - Prob. 19QPCh. 20 - Prob. 20QPCh. 20 - Prob. 21QPCh. 20 - Prob. 22QPCh. 20 - Prob. 23QPCh. 20 - Prob. 24QPCh. 20 - Prob. 25QPCh. 20 - Prob. 26QPCh. 20 - Prob. 27QPCh. 20 - Prob. 28QPCh. 20 - Prob. 29QPCh. 20 - Prob. 30QPCh. 20 - Prob. 31QPCh. 20 - Prob. 32QPCh. 20 - Prob. 33QPCh. 20 - Prob. 34QPCh. 20 - Prob. 35QPCh. 20 - Prob. 36QPCh. 20 - Prob. 37QPCh. 20 - Prob. 38QPCh. 20 - Prob. 39QPCh. 20 - Prob. 40QPCh. 20 - Prob. 41QPCh. 20 - Prob. 42QPCh. 20 - Prob. 43QPCh. 20 - Prob. 44QPCh. 20 - Prob. 45QP
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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
- The Sun orbits the center of the Galaxy in 225 million years at a distance of 26,000 light-years. Given that a3=(M1+M2)P2 , where a is the semimajor axis and P is the orbital period, what is the mass of the Galaxy within the Sun’s orbit?arrow_forwardSuppose three stars lie in the disk of the Galaxy at distances of 20,000 light-years, 25,000 light-years, and 30,000 light-years from the galactic center, and suppose that right now all three are lined up in such a way that it is possible to draw a straight line through them and on to the center of the Galaxy. How will the relative positions of these three stars change with time? Assume that their orbits are all circular and lie in the plane of the disk.arrow_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
- 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 itarrow_forwardThe figure below shows the spectra of two galaxies A and B.arrow_forwardA star at a distance of 50000 light years from the center of a galaxy has an orbital speed of 100 km/s around the galactic center. What is the total mass of the galaxy located at distances smaller than 50000 light years from the center? A. 7.6 ×1010 solar masses B. 4.2 ×1011 solar masses C. 3.5 ×1010 solar masses D. 1.4 ×1011 solar masses Is the answer C? M = (r x v^2) / G = 50000 x 9.46e15 x (100000^2) / 6.67e-11 / 2e30 (the Sun's mass) = 3.55e10 solar massesarrow_forward
- A galaxy's rotation curve is a measure of the orbital speed of stars as a function of distance from the galaxy's centre. The fact that rotation curves are primarily flat at large galactocen- tric distances (vrot(r) ~ constant) is the most common example of why astronomer's believe 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 rotation curve. (b) Show that a p(r) ∞ r¯² density profile successfully produces a flat ro- tation curve and must therefore be the general profile that dark matter follows in our galaxy.arrow_forwardSuppose that the outer stars of a galaxy have an orbital velocity of 150 km/s. If the radius of the galaxy is 4.0 kpc (1??? = 3.1 × 1016 ??), what is the orbital period of the outer stars in years?arrow_forwardAs we discussed, clouds are made of a great many small drops. Really - a great many. Imagine a liquid cloud that fills a volume of 1 km3. The clouds contains 100 drops per cubic centimeter; for the sake of argument assume that each is 10 microns (micrometers) in radius. A. How many drops does the cloud contain? Compare this to a big number - say, the number of stars in the galaxy. B. What mass of water does the cloud contain? Compare this to something big - elephants, trucks, that sort of thing. C. What fraction of the cloud volume is filled with condensed water? One way to approach this is to compare the density of the suspended liquid water to the density of the surrounding air. D. How many 1 mm drizzle drops could you make from all the cloud drops? E. How much energy was released when this water condensed from vapor to liquid? If the water condensed in 20 minutes (a reasonable lifetime for a small cloud), what was the (energy per time)? powerarrow_forward
- Among 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_forwardGlobular 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)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_forward
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