UNDERSTANDING THE UNIVERSE(LL)-W/CODE
3rd Edition
ISBN: 9780393869903
Author: PALEN
Publisher: NORTON
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Question
Chapter 15, Problem 40QAP
To determine
The time taken by globular cluster to complete one trip around the center of the galaxy.
(b)
To determine
The number of rotation since the given time.
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A 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 masses
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-…
What 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 these
Chapter 15 Solutions
UNDERSTANDING THE UNIVERSE(LL)-W/CODE
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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