Bundle: Foundations of Astronomy, Enhanced, Loose-Leaf Version, 13th + MindTap Astronomy, 2 terms (12 months) Printed Access Card
13th Edition
ISBN: 9781337214353
Author: Seeds, Michael A., Backman, Dana
Publisher: Cengage Learning
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Question
Chapter 16, Problem 15P
To determine
The estimated mass of the galaxy and the assumptions depends on this mass.
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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 = 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.
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
Sun. All distances are expressed in kpc. An astronomer observes the
center of the Galaxy within a small field of view. We take a particular
type of Red giant stars as the standard candles for the observation with
approximately constant absolute magnitude of M = -0.2,
(a) A telescope has a limiting magnitude of m = 18. Calculate the
maximum distance to which this telescope can detect these red
giant stars. For simplicity we ignore the presence of interstellar
medium so there is no extinction.
(b) Assume an extinction of 0.7 mag/kpc for the interstellar medium.
Repeat the calculation as done in the part 5a and obtain a rough
number for the maximum distance these red giant stars can be
observed.
(c) Give an expression for the number of these red giant stars per mag-…
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 16 Solutions
Bundle: Foundations of Astronomy, Enhanced, Loose-Leaf Version, 13th + MindTap Astronomy, 2 terms (12 months) Printed Access Card
Ch. 16 - Prob. 1RQCh. 16 - Of the nearby galaxies, which is the most common...Ch. 16 - Prob. 3RQCh. 16 - My center is round, and I have no spiral arms...Ch. 16 - Prob. 5RQCh. 16 - Which are more common, barred or nonbarred spiral...Ch. 16 - Prob. 7RQCh. 16 - Prob. 8RQCh. 16 - Prob. 9RQCh. 16 - Prob. 10RQ
Ch. 16 - Prob. 11RQCh. 16 - Prob. 12RQCh. 16 - Prob. 13RQCh. 16 - Prob. 14RQCh. 16 - Prob. 15RQCh. 16 - Prob. 16RQCh. 16 - Prob. 17RQCh. 16 - Prob. 18RQCh. 16 - Prob. 19RQCh. 16 - Prob. 20RQCh. 16 - Prob. 21RQCh. 16 - What is the percentage range of galaxy diameters...Ch. 16 - What is the percentage range of galaxy masses...Ch. 16 - Prob. 24RQCh. 16 - Prob. 25RQCh. 16 - Prob. 26RQCh. 16 - Prob. 27RQCh. 16 - Prob. 28RQCh. 16 - Prob. 29RQCh. 16 - Prob. 30RQCh. 16 - Prob. 31RQCh. 16 - Prob. 32RQCh. 16 - Prob. 33RQCh. 16 - Prob. 34RQCh. 16 - Prob. 1DQCh. 16 - Prob. 2DQCh. 16 - Prob. 3DQCh. 16 - Prob. 4DQCh. 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. 10PCh. 16 - Prob. 11PCh. 16 - Prob. 12PCh. 16 - Prob. 13PCh. 16 - Prob. 14PCh. 16 - Prob. 15PCh. 16 - Prob. 16PCh. 16 - Prob. 1LTLCh. 16 - Prob. 2LTLCh. 16 - Prob. 3LTLCh. 16 - Prob. 4LTLCh. 16 - Prob. 5LTLCh. 16 - Prob. 6LTL
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- Suppose 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_forwardPretend that galaxies are spaced evenly, 7.0 Mpc apart, and the average mass of a galaxy is 1.0 ✕ 1011 M. What is the average density (in kg/m3) of matter in the universe? (Note: The volume of a sphere is 4/3pieR^3 and the mass of the sun is 2.0 ✕ 1030 kg.) ______ kg/m^3 Which model universe does this density value support? A: open B: flat C: closedarrow_forwardgiven: a (distance to center of galaxy in AU) = 1,717,914,439 AU P (suns orbital period in years) = 203,782,828.3 years M (mass of milky way galaxy in solar masses) = 1.22 x 10^11 Msun Question: Assume the Milky Way Galaxy is made up entirely of stars like the Sun, i.e. on average each star has the mass of 1 MSun. Under this assumption, approximately how many stars are there in our galaxy? Express this answer in billions of stars (1 billion = 109).arrow_forward
- In the reading, you were told that there were roughly 10,000 galaxies in the image of the Hubble Ultra Deep Field alone. The image is roughly 10 square arcminutes and there are roughly 1.5*10^8 square arcminutes composing the entire sky. With that in mind and assuming that the Hubble Ultra Deep Field represents an average part of the sky, roughly how many galaxies may exist in the observable universe? (Please include commas for every factor of 1,000; for example 2,343,567,890)arrow_forwardIf astronomers were to find they have made a mistake and our solar system is actually 7.8 (rather than 8.2) kpc from the center of the galaxy, but the orbital velocity of the sun is still 240 km/s, what is the minimum mass of the galaxy? (Hint: Use Kepler's third law.)arrow_forwardIf the active core of a galaxy contains a black hole of 106 M, what will the orbital period be for matter orbiting the black hole at a distance of 0.23 AU? Hint: Use the formula for circular velocity, V. GM V hrarrow_forward
- Our galaxy is approximately 100,000 light years in diameter and 2,000 light years thick through the plane of the galaxy. If we were to compare the ratio of the diameter galaxy and its thickness to the ratio of the diameter of a CD and its thickness (CD has a diameter of 12 cm and thickness of 0.6 mm), what would be the factor differentiating those ratios? Put differently, if the galaxy were scaled down to the diameter of a CD, how many times thicker or thinner would the galaxy be than the CD? (For example if it would be twice as thick, you would answer 2 and if it were twice as thin you would answer 0.5 (aka 1/2))arrow_forwardThe density profile of a galaxy's extended dark matter halo is given in the provided image. r0 and ρ0 are both constant. r is the distance from the center of the halo. Find the mass of dark matter inside a sphere with radius R around the center.arrow_forwardIf you find a galaxy that is the same size and mass as our Milky Way Galaxy, what orbital velocity would a small satellite galaxy have if it orbits 51 kpc from the center of the larger galaxy? (Assume the total mass of our galaxy is about 4.0 1011 solar masses, M.)arrow_forward
- If the active core of a galaxy contains a black hole of 106?Θ (1 million solar masses), what will the orbital velocity be for matter orbiting the black hole at a distance of 0.33 AU? (Hint: use the formula for orbital velocity: ?=√???; where ?=6.67×10−11 ?3?? ?2 and ?Θ= 2.0×1030 ??. Note: 1 ??=1.50×1011 ?)arrow_forwardthe sun has an orbital speed of about 220kms^-1 around the centre of the galaxy , whose distance is 28 000 light years.estimate the total mass of the galaxy in solar massesarrow_forwardGiven an image of a disk galaxy, you have measured that the average surface brightness at two radii (R = R1 and R = R2) are I1 and I2 respectively. The disk surface brightness profile has the exponential form of I(R) = I0 e(-R/Rd). What are the values of I0 and Rd for this disk?arrow_forward
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