Star evolution
Chapters 17 & 18
(Yes, we skip chap. 16, star birth)
Goals & Learning Objectives
• Learn some simple astronomical terminology
• Develop a sense of what scientists know about
the overall universe, its constituents, and our
location
• Describe stellar evolution
• Contrast the life history of a low-mass star
with the life history of a high-mass star.
• Explain how black holes are formed and their
effect on their surrounding environment.
3 star groups (p. 565)
•
3 categories of stars:
–
–
–
•
•
Intermediate similar to both high and low mass. Book
focuses more on similarities with high mass (in section
17.1).
One major difference: __________________________
___________________________________
Which star group has the highest core
pressure?
1. Low mass
2. Intermediate mass
3. High mass
0
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Which star group has the hottest core
temperature?
1. Low mass
2. Intermediate mass
3. High mass
0
0
0
So what can you conclude about the fusion rate? Luminosity?
Which stars live longer? Why?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
The end of the Sun
•
•
•
•
•
•
•
•
•
Eventually ________________________.
What did the core need fusion for?
What will happen to it as a result of ___________?
What happens to __________________________?
What happens to the temperature of the material
surrounding the core?
CLICKER QUESTION (next slide).
What are the surrounding layers made of?
What can happen if ________________________?
For Sun, this takes ___________________of years.
Is there Hydrogen outside the Sun’s core?
1. Yes
2. No
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
_______________________
•
•
•
•
•
•
•
•
•
In fact, the outer layers get hotter than _________.
What does that tell us about ______________rate?
What should we observe as a result? CLICKER
The light “gets stuck” and pushes the outer layers
out.
What happens to gas when you _______________?
Color of outside? What kind of star do we have?
What is the core made of?
What is the structure?
See fig. 17.4 page 568
Star becomes ______ luminous
1. More
2. Less
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
What’s happening to the mass of the
HELIUM core as the shell “burns”?
1. Increasing
2. Decreasing
3. Staying the same
0
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Inside the core…
•
•
•
•
_______________________
Core _____________________
More hot helium dumped onto core
_________________________________from shrinking.
– _____________stars: ________________________________
• Read section 16.3, page 557 and S4.4 pp. 481-483
• ______________________
–
Intermediate &
High mass _______________ thermal & _____________.
• _______________________turns on at 100 million K
– Low mass: whole _____________simultaneously: _____________
– Intermediate & high mass: “regular” fusion
Next phase
•
•
•
•
Structure of the star now?
Figure 17.5
This lasts until …
What happens to the core?
– Low & intermediate mass: ____________until ___________
______________stops it. Focus on that now.
– [for High mass: ___________________________]
• Back to low mass: What’s the core made of?
• Shrinks to size of Earth.
• What happens outside the core?
– Temp, composition
__________________burning
•
•
•
•
Not stable
Outer layers ________________
Outer layers _______________
See pictures around the planetarium
– Cat’s eye, Butterfly, Ring: all “________________________”
•
•
•
•
•
See also figure 17.7 – more examples
NOT related to planets
What’s in the center of a planetary nebula?
End of low & intermediate mass stars…
Show interactive figure 17.4
Do low mass stars like the Sun fuse Carbon into
anything?
1. Yes
2. No
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
If the universe contained only low mass stars, would
there be elements heavier than carbon?
1. Yes
2. No
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
High mass star differences
• ____________________________________
– Gas & thermal pressure always stronger
•
•
•
•
Can fuse carbon with helium into Oxygen
Can fuse Oxygen with helium into neon
Etc. (magnesium, silicon, sulfur)
When core hot enough, can fuse carbon with carbon,
carbon with oxygen …
• Etc.
• Big picture: carbon and stuff fuses until you get to a
core made of …
• Iron (Fe on the periodic table, #26, middle section,
top row, see page A-13, Appendix C)
Iron
• Most stable nucleus
• _____________________________________
– _________________energy (uses instead of ___________)
• True for everything heavier than iron, too.
– Fission USES energy
• True for most things lighter than iron, too.
• Iron is the last element made in stable reactions in
stars
• Look at the periodic table on page A-13
– Find iron
– Gold = Au. Mercury = Hg. Xenon = Xe. Are these made in
stable stars?
What we see
• See figure 17.12, page 575 for onion skin
model
• See HR diagram on p. 575 (fig. 17.13)
– Runs out of core fuel, goes right
– Next fuel turns on, goes back left
– Repeat until core is made of Iron
•
•
•
•
•
After the Iron core forms
Iron core __________________
________________than ________________________pressure
_________________________more than they can tolerate
Electrons merge with protons
Result: _______________
– And ___________________!
– (Fly straight out! We observe them first!)
•
•
•
•
•
•
•
•
________more electron degeneracy _______________support.
Rapidly shrinks: ___________________________in 1 second!
Lots of energy released. Turn on neutron degeneracy pressure.
___________________________. Demo
______________________________. Leaves behind core
Core is made of … Called …
Interactive figure 17.12 & 17.17 (crab nebula in 1054)
(If the core is too heavy for neutron degeneracy pressure…)
Production of Elements
• High mass stars make up to _________
• _______________________made _________
__________________
– Lots of neutrons around
– They merge with nuclei quickly (r-process)
– Eventually nucleus decays to something stable
– Like _________________________________, etc.
Stellar remnants
• End states for stars
– Low mass stars become …
– Intermediate mass also become … (Oxygen)
– & high mass stars become …
– The highest mass stars (O & B) become …
Which stars should begin with the most
heavy elements inside them?
1. The stars that formed earliest
2. The most recently formed stars
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Summary of star death
•
•
•
•
•
•
•
When fusion runs out, core ____ & _____
Shell fusing occurs. Many shells possible.
Core fusion can turn on.
What’s different for low mass & high mass?
Which elements get made in low & high?
What’s special about iron?
Degeneracy pressure (electron & neutron)
– What, where, why
• Possible end states; which stars make them
– RG  PN  WD, RG  SN  NS or BH
Chapter 18: Stellar remnants
• The next few slides are material from chap 18.
White dwarfs
• Radius
– ______________________________________
• What kind of pressure resists gravity?
– _________________________________pressure
• Temperature
– Start ______________. [Clicker question]
– Cool down (__________________eventually)
• Composition:
– Usually _____________________
– sometimes oxygen (intermediate mass) or helium (very
low mass)
• Gravity: teaspoon weighs _______________!
What kind of light would a white dwarf emit
most when it is first detectable?
1.
2.
3.
4.
0
0
0
0
X-rays
Visible light
Infrared
Radio waves
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
White dwarf limit
• Observed around _______________
• Can be up to ______________
• If heavier, _________________________strongly enough to
resist gravity. [they’d have to move faster than c]
• What happens if you add mass to a 1.4 Msun white
dwarf?
– Where could extra mass come from?
– _____________________________!
– _________________________________ (“Type 1a”)
• Are a “standard candle”. What’s that?
– Leaves NOTHING behind, _________________________
– LESS VIOLENT: Nova if add small amount of stuff to lower
mass WD.
Sirius binary system
What you’d see through a telescope
Ignore the spikes
X-ray image & visible image
superimposed
Neutron stars
• Composition?
– Gigantic nuclei.
– No empty space like in atoms (99.999% empty)
• Paper clip of neutrons weighs as much as ______________!
• Dropping brick: energy = an atom _____________!
– As stuff falls onto a neutron star, ________________________!
• Mass
– Observed: __________________________________
– Can be up to _______________(we don’t know exact upper limit)
– Any heavier & ____________________________strongly enough
to resist gravity.
• Radius: City sized (_______________). WD = _______miles!
• What kind of pressure resists gravity?
– _______________________pressure
• Neat trivia: Escape speed = ½ c. (Gravity very strong!)
Pulsars
•
•
•
•
•
See figures 18.7 & 18.8
Jocelyn Bell
Should’ve won the Nobel Prize
Rapidly spinning neutron stars
1800 known pulsars, pulsing radio, but some also emit
other types: visible + X-rays and sometimes gamma.
– 1 pulsar, discovered in October 2008 emits only gamma
• See figure 18.9
• Is it possible to be a neutron star that’s not a pulsar? How
about vice versa? [2 clicker Q’s]
• Spin up to 600 times per SECOND! (Show movie!)
– Larger objects would break apart
Is it possible to be a neutron star but not a
pulsar, as seen on Earth?
1. Yes
2. No
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Is it possible to be a pulsar but not a
neutron star, as seen on Earth?
1. Yes
2. No
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Black holes – Remind me to reveal the
information as your questions are
answered
Chap. 18, #18: If a black hole 10 times as massive as our Sun
were lurking just beyond Pluto’s orbit, we’d have no way of
knowing it was there.
1. True
2. False
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Summary of stellar “graveyard”
•
•
•
•
•
White dwarf properties: mass, radius, pressure
White dwarf limit, results of exceeding it
Neutron star properties
Pulsars
Black holes
– Falling in
– Gravity far away
– How we can find them