Download HW #8

Astronomy Assignment #08 Other Galaxies
Your Name______________________________________
Your Class Meeting Time __________________________
This assignment is due on __________________________
Submit this cover sheet with your assignment.
Complete the assigned problems from the text listed below and address the Instructor Assigned Topic.
Mathematical problems may be hand written. Write out the problem, show your work in solving the problem
and state your answer in a complete sentence. Failure to complete all three of these tasks will result in less
than full credit awarded. The Instructor assigned topic must be typed.
Read Chapter 15 in Astronomy Notes;
Introduction
Other Galaxies
Types of Galaxies
Ellipticals
Spirals
Irregulars
Positions On Our Sky
Review Questions
Distances to Galaxies
Hubble Law
Masses of Galaxies
Clusters of Galaxies
Dark Matter in Galaxy Clusters
Superclusters
Galaxy Origins
Galaxy Collisions and Mergers
Review Questions
1. What separates a cluster of stars from a galaxy?
2. What are four basic distinguishing characteristics between a spiral galaxy and an elliptical galaxy?
What kind of galaxy do we live in?
3. What is the most common type of galaxy? How does their proportion in the universe compare with the
proportion of them shown in astronomy books? Explain any differences there may be.
4. Why are irregular galaxies called irregulars?
5. Why do you see more galaxies when you look in a direction perpendicular to the Galactic plane than
when you look along Galactic plane?
6. Why must the distance to a galaxy be known first before you can measure such basic properties of the
galaxy such as its luminosity, mass, and size?
7. What are the various ways you can find distances to the galaxies?
8. What do you find when you plot the redshifts of the galaxies vs. their distance from us? How does the
speed of most galaxies vary with increasing distance from our galaxy?
9. How does the Hubble Law show that the universe is expanding?
10. How does the Hubble Law show that all of the galaxies are moving away from each other and that
astronomers in every galaxy will see the same Hubble law?
11. How can you measure the masses of galaxies?
12. What is it about the motions of the stars in galaxies that indicates a large amount of dark matter is
present?
13. What is a cluster of galaxies? Are we in one? What is the nearest large cluster of galaxies to us?
14. Why are collisions of galaxies much more common than collisions of stars?
15. How are spiral galaxies formed?
16. What two ways are there to create an elliptical galaxy?
17. What kind of galaxy is typically found near the center of a large cluster of galaxies? Why is that kind of
galaxy so big?
Instructor Assigned Topic:
This portion of the assignment tasks you with characterizing the galaxies in the Local Group of
Galaxies. Write a summary of the Local Group using the table of Local Group Galaxy Properties below.
Include a paragraph that describes the “average” galaxy in the Local Group.
The Local Group of Galaxies
Source: http://nedwww.ipac.caltech.edu/level5/Mateo/table1.html
Galaxy
1
38
2
3
4
5
6
7
8
9
10
11
32
12
13
14
21
18
19
20
15
16
17
22
24
23
26
25
40
39
27
28
37
36
33
41
35
34
30
29
31
Milky Way
Sagittarius (SagDEG)
LMC
SMC
Ursa Major/Minor?
Draco
Sculptor
Carina
Sextans
Fornax
Leo I
Leo II
Phoenix
NGC 6822
WLM
IC 5152
M 31
M 32
NGC 147
NGC 185
And II
And III
And I
NGC 205
M 33
IC 1613
DDO 210
LGS 3
Tucana
SagDIG
GR 8
IC 10
Sextans A
Antila
EGB 0427+63
UKS 2323-326
NGC 3109
Sextans B
Pegasus
Leo A
NGC 55
Type
Sbc
dE-N
Irr III-IV
Irr IV-V
dE
dE
dE
dE
dE
dE
dE
dE
dIrr/dE
Irr IV-V
Irr IV-V
dIrr
Sb I-II
E2
dE/dE5
dE/dE3p
dE
dE
dE
E5p/dE-N
Sc II-III
Irr V
dIrr/dE
dIrr IV-V
dE
dIrr
dIrr
dIrr
dIrr
dIrr/dE
dIrr
dIrr
Irr IV-V
dIrr
dIrr/dE
dIrr
Irr IV
Apparent Distance, Absolute Diameter,
Magnitude
kpc
Magnitude
kpc
3.5
0.6
2.8
11.6
12.0
9.1
13.0
10.2
8.5
11.8
12.3
13.1
9.3
11.3
11.7
4.4
9.0
10.4
10.1
14.0
14.0
14.0
8.6
6.3
10.0
15.3
15.5
15.7
12.9
14.6
11.7
11.9
14.7
13.0
13.6
10.0
11.8
12.4
12.7
8.8
0
25
50
63
90
90
100
100
100
150
180
180
445
521
610
610
670
670
670
670
670
670
670
675
770
770
920
920
980
1,060
1,227
1,227
1,230
1,235
1,300
1,320
1,380
1,440
1,534
1,534
2,150
-20.6
-13.4
-18.4
-17.0
-8.2
-8.0
-10.6
-5.5
-9.5
-12.9
-9.6
-9.2
-10.1
-15.1
-15.0
-14.6
-21.6
-15.5
-14.4
-14.6
-10.6
-10.6
-10.6
-15.7
-19.1
-14.5
-11.0
-9.7
-9.6
-12.3
-11.0
-16.2
-14.6
-10.8
-12.6
-12.0
-15.7
-14.2
-13.4
-13.5
-18.0
36.0
3.0
19.0
8.0
1.4
1.8
1.0
2.0
2.0
0.5
0.3
2.0
1.1
2.5
0.5
7.3
32.0
2.5
3.7
3.9
0.7
0.9
0.9
3.1
11.0
3.8
0.4
0.2
1.4
0.5
0.1
1.8
2.1
1.8
0.4
0.5
6.4
2.1
2.5
2.1
21.3
Radial
Velocity,
km/s
0
80
12
-30
17
-31
162
230
230
-51
285
70
66
11
74
-59
35
89
39
-1
3
-125
11
-79
324
-82
62
131
300
129
Galactic
X, kpc
Galactic
Y, kpc
Galactic
Z, kpc
0.0
23.6
7.7
24.4
-16.5
4.6
3.6
-15.9
-33.0
-33.5
-81.9
-53.3
6.1
446.9
42.0
375.2
-322.7
-321.8
-322.7
-332.1
-367.3
-294.2
-319.3
-321.5
-453.6
-242.0
651.7
-416.6
529.1
949.2
180.0
-593.9
-380.8
-137.3
-1,043.2
422.6
-174.5
-622.6
-93.1
-895.5
471.9
0.0
2.3
-41.3
-37.9
61.7
73.8
-11.3
-91.2
-66.2
-51.8
-84.8
-45.0
-160.1
211.3
167.0
-108.3
532.8
531.4
563.4
557.2
455.2
524.3
517.1
541.5
476.3
290.4
439.6
556.8
-400.1
366.3
-209.3
1,071.4
-863.4
-1,134.4
738.6
89.1
-1,257.3
-832.2
1,108.8
-272.1
-243.6
0.0
-6.0
-27.2
-44.0
63.4
51.2
-99.3
-37.8
67.3
-136.7
136.1
165.9
-415.2
-164.5
-585.2
-468.7
-246.6
-251.0
-165.5
-167.8
-326.9
-295.8
-282.1
-243.0
-400.4
-670.8
-478.0
-602.4
-721.4
-297.5
1,195.6
-70.6
789.0
468.6
236.9
-1,247.3
541.4
996.7
-1,055.9
1,215.4
-2,083.4
Apparent Distance, Absolute Diameter,
Magnitude
kpc
Magnitude
kpc
Mean Properties
Max
Min
10.9
15.7
0.6
724
2,150
0
-13.2
-5.5
-21.6
4.7
36.0
0.1
Galaxy Type Ledgend
dE - Dwarf Elliptical
dIrr - Dwarf Irregular
E - Elliptical
Irr - Irregular
S - Spiral
SB - Barred Sprial
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