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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Question
Chapter 17, Problem 3TY
To determine
The reason for a galaxy such as M31 (Andromeda) to have a blueshift instead of a redshift.
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A Type la supernova explodes in a galaxy at a
distance of 6.10×107 light-years from Earth. If
astronomers detect the light from the
supernova today, how many years T have
passed since the supernova exploded? T=
2.07 x10 -5 years Given a Hubble constant of
74.3 km/s/Mpc, at what speed v is this galaxy
moving away from Earth? v= km/s What is
this galaxy's redshift? redshift:
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…
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.
Chapter 17 Solutions
Loose Leaf For Explorations: Introduction To Astronomy
Ch. 17 - Prob. 1QFRCh. 17 - Prob. 2QFRCh. 17 - Prob. 3QFRCh. 17 - Prob. 4QFRCh. 17 - (17.3) Why are galaxy collisions of interest?Ch. 17 - Prob. 6QFRCh. 17 - Prob. 7QFRCh. 17 - Prob. 8QFRCh. 17 - Prob. 9QFRCh. 17 - Prob. 10QFR
Ch. 17 - Prob. 11QFRCh. 17 - Prob. 12QFRCh. 17 - Prob. 13QFRCh. 17 - Prob. 14QFRCh. 17 - Prob. 15QFRCh. 17 - Prob. 16QFRCh. 17 - Prob. 17QFRCh. 17 - Prob. 18QFRCh. 17 - Prob. 19QFRCh. 17 - Prob. 20QFRCh. 17 - Prob. 21QFRCh. 17 - Prob. 22QFRCh. 17 - Prob. 1TQCh. 17 - Prob. 2TQCh. 17 - Prob. 3TQCh. 17 - Prob. 4TQCh. 17 - Prob. 5TQCh. 17 - Prob. 6TQCh. 17 - Prob. 1PCh. 17 - Prob. 2PCh. 17 - Prob. 3PCh. 17 - Prob. 4PCh. 17 - Prob. 5PCh. 17 - Prob. 6PCh. 17 - Prob. 7PCh. 17 - Prob. 8PCh. 17 - Prob. 9PCh. 17 - Prob. 10PCh. 17 - Prob. 1TYCh. 17 - Prob. 2TYCh. 17 - Prob. 3TYCh. 17 - Prob. 4TYCh. 17 - Prob. 5TYCh. 17 - Prob. 6TYCh. 17 - Prob. 7TYCh. 17 - Prob. 8TYCh. 17 - Prob. 9TYCh. 17 - Prob. 10TY
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- 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.arrow_forwardIt is possible to derive the age of the universe given the value of the Hubble constant and the distance to a galaxy, again with the assumption that the value of the Hubble constant has not changed since the Big Bang. Consider a galaxy at a distance of 235 million light-years receding from us at a velocity, v. If the Hubble constant is 20.5 km/s per million light-years, what is its velocity? (Enter the magnitude in km/s.) _________ km/sarrow_forwardAre the galaxies red-shifting or blue-shifting? Explain. (You may find the big-bang theory helpful). Andromeda galaxy is currently approaching our galaxy with a radial velocity of 266 km/sec. How far is our galaxy from Andromeda? (Hubble’s constant, H, is 73 km/sec/MParsec). When can the two galaxies be anticipated to collide?arrow_forward
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