Download Gold ( 197 Au)

Creation of new elements is energy source of stars (and the sun)
“We are made of star stuff….” Carl Sagan
The sun shines
3.85e33 erg/s = 3.85e26 Watts
for at least ~4.5 bio years
The entire sun made of coal would last ~ 4000 years
Nucleus
Factories
Committee for the Physics of the Universe (NRC/NAS)
“Connecting Quarks with the Cosmos” – 11 science questions for the new century
Question 3
How were the elements from
iron to uranium made ?
(main question: r-process)
Periodic Table of Elements in nature
Elements in nature
Made in the Big Bang
Elements in nature
Made by fusion in stars…
Elements in nature
How are the elements heavier than iron made?
Burning stages of a 25 solar mass star
initially present: mostly hydrogen (~70% - from big bang)
Hydrogen burning
7Mio yrs
Hydrogen (1p,0n)
Helium (2p, 2n)
Helium burning
700,000 yrs
Helium (2p,2n)
Carbon (6p, 6n), Oxygen (8p,8n)
Carbon(+Ne) burning
400 yrs
Carbon (6p,6n)
Oxygen (8p,8n)
Oxygen burning
8 months
Oxygen (8p,8n)
Silicon (14p,14n)
Silicon burning
1 day
Silicon (14p,14n)
Nickel (28p,28n)
For stable nuclei !!!
Window of the Protestant church in Wixhausen, Germany
Precollapse structure of massive star
Iron core collapses and triggers supernova explosion
Atomic Nucleus
Proton
Neutron
What is the universe made of?
Observed Nuclei in the Universe:
1.0
91.0%
number fraction
0.8
0.6
Iron ?
0.4
8.9%
0.2
0.0
0
Hydrogen:
Mass number = 1
50
100
150
mass number
Helium:
Mass number = 4
200
250
What is the Universe made of?
Iron:
Gold:
26 protons + 30 neutrons
79 protons + 118 neutrons
Mass number = 56
Mass number = 197
number fraction
0
10
-1
10
-2
10
-3
10
-4
10
-5
10
-6
10
-7
10
-8
10
-9
10
-10
10
-11
10
-12
10
-13
10
0
50
100
150
mass number
200
250
92
The origin of gold - the path of nucleosynthesis
90
88
86
84
197Au: Au
has 79 protons
197Au has 197 – 79 = 118 neutrons
82
80
78
76
74
Gold
72
70
(197Au)
68
66
64
number of protons
62
60
58
56
128 1
54
52
50
120
48
116
46
44
112
108
42
100
40
88
38
36
92
84
34
32
30
76
28
80
72
26
68
24
56
22
60
64
20
52
18
16
14
12
48
44
36
10
8
16
12
2
0
4
0
40
32
6
4
8
20
24
96
28
Helium
Hydrogen
number of neutrons
104
124
92
The origin of gold - the path of nucleosynthesis
90
88
86
84
197Au: Au
has 79 protons
197Au has 197 – 79 = 118 neutrons
82
80
78
76
74
Gold
72
70
(197Au)
68
66
64
number of protons
62
60
58
56
128 1
54
52
50
120
48
116
46
44
112
108
42
100
40
88
38
36
92
84
34
32
30
76
28
80
72
26
68
24
56
22
60
64
20
52
18
16
14
12
48
44
36
10
8
16
12
2
0
4
0
40
32
6
4
8
20
24
96
28
Helium
Hydrogen
number of neutrons
104
124
So how is gold made ?
Some earlier failed attempts (1590)
… by Alchemy:
For example:
with the “Philosopher’s Stone”
Making gold/silver from base metals
NSCL (present day)
… by a nuclear reaction
for example:
208Pb + 9Be -> 197Au + p + ….
Makes gold from lead…
at a very slow rate
(20,000 nuclide/sec)
Alchemists lab + NSCL
Iron from a previous generation of stars is exposed to a flux of neutrons
How does this create heavy elements ?
 Neutron Capture Processes
There are 2:
- s-process (slow neutron capture)
- r-process (rapid neutron capture)
Do neutron capture process exercise
Where does the s-process happen ?
there !
in red giants – and it takes several million years !
(or, low mass TP-AGB stars)
AGB = Asymptotic Giant Branch
TP=Thermally Pulsing
How can we tell ?
Analyze light from a red giant:
Star contains Technetium (Tc) !!!
(heavy element Z=43, T1/2 4 Mio years, Merrill 1952)
92
The origin of gold - the path of nucleosynthesis
90
88
86
84
197Au: Au
has 79 protons
197Au has 197 – 79 = 118 neutrons
82
80
78
76
74
Gold
72
70
(197Au)
68
66
64
number of protons
62
60
58
56
128 1
54
52
50
120
48
116
46
44
112
108
42
100
40
88
38
36
92
84
34
32
30
76
28
68
24
56
22
20
18
16
14
12
44
36
16
12
2
0
64
52
40
32
6
4
4
?
60
48
8
0
80
72
26
10
8
20
24
96
28
Helium
Hydrogen
number of neutrons
104
124