21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Chapter 21, Problem 25QP
To determine
Explain the reason why the relationship between recession velocity and redshift fails for distant galaxies.
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A galaxy with a spherically symmetric distribution of matter has a mass density profile of the type p(r) ∞ 1/r, where r is the radial coordinate from the centre
of the galaxy. To what type of circular velocity (r) does this correspond?
Select one:
a. (r)
O b.
c.
O d.
(r) ~ r
(r) ~ √r
(r): = constant
An observational survey of distant galaxies is undertaken that involves measuring their
distances using cepheid variables and red-shifts using spectroscopy. Explain how cepheid
variables can be used to measure the distances to galaxies.
A spectral line is observed whose wavelength in the laboratory is de
length of this spectral line observed in each galaxy, Xo, is listed in the table, along with
the distance, d, to the galaxy. Determine the red-shift and the recession velocity of each
galaxy and tabulate your results by making a copy of the table and filling in the blank spaces.
Sketch a Hubble diagram using your results and determine the value of the Hubble constant
Ho in units of km s-1 Mpc.
650 nm. The wave-
Galaxy 1
652.69
Galaxy 2 Galaxy 3 Galaxy 4 Galaxy 5
653.01
do (nm)
d (Mpc)
658.54
662.18
681.63
17
19
54
77
200
v (km s-1)
(a) Estimate the height (z) above or below the Galactic plane for the globular cluster
M13 (1,b = 59°, 40.9°) and the Orion Nebula (1,b = 209°, -19.4°). M13 and the Orion
Nebula are 7 kpc and 450 pc away from Earth respectively.
(b) To which components of the Galaxy do these objects probably belong? Explain your
answers.
Chapter 21 Solutions
21st Century Astronomy
Ch. 21.1 - Prob. 21.1CYUCh. 21.2 - Prob. 21.2CYUCh. 21.3 - Prob. 21.3ACYUCh. 21.3 - Prob. 21.3BCYUCh. 21.4 - Prob. 21.4CYUCh. 21 - Prob. 1QPCh. 21 - Prob. 2QPCh. 21 - Prob. 3QPCh. 21 - Prob. 4QPCh. 21 - Prob. 5QP
Ch. 21 - Prob. 6QPCh. 21 - Prob. 7QPCh. 21 - Prob. 8QPCh. 21 - Prob. 9QPCh. 21 - Prob. 10QPCh. 21 - Prob. 11QPCh. 21 - Prob. 12QPCh. 21 - Prob. 13QPCh. 21 - Prob. 14QPCh. 21 - Prob. 15QPCh. 21 - Prob. 16QPCh. 21 - Prob. 17QPCh. 21 - Prob. 18QPCh. 21 - Prob. 19QPCh. 21 - Prob. 20QPCh. 21 - Prob. 21QPCh. 21 - Prob. 23QPCh. 21 - Prob. 24QPCh. 21 - Prob. 25QPCh. 21 - Prob. 26QPCh. 21 - Prob. 27QPCh. 21 - Prob. 28QPCh. 21 - Prob. 29QPCh. 21 - Prob. 30QPCh. 21 - Prob. 31QPCh. 21 - Prob. 32QPCh. 21 - Prob. 33QPCh. 21 - Prob. 34QPCh. 21 - Prob. 35QPCh. 21 - Prob. 36QPCh. 21 - Prob. 37QPCh. 21 - Prob. 38QPCh. 21 - Prob. 39QPCh. 21 - Prob. 40QPCh. 21 - Prob. 41QPCh. 21 - Prob. 42QPCh. 21 - Prob. 43QPCh. 21 - Prob. 44QPCh. 21 - Prob. 45QP
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