creation of new elements is energy source of stars (and the sun) we are made of star stuff…. carl...
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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
NucleusFactories
Question 3How were the elements from
iron to uranium made ?(main question: r-process)
Question 3How were the elements from
iron to uranium made ?(main question: r-process)
Committee for the Physics of the Universe (NRC/NAS)
“Connecting Quarks with the Cosmos” – 11 science questions for the new century
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?
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)
Burning stages of a 25 solar mass star
initially present: mostly hydrogen (~70% - from big bang)
For stable nuclei !!!
Ave
rage
bin
ding
ene
rgy
per
nucl
eon
(MeV
)
Window of the Protestant church in Wixhausen, Germany
Precollapse structure of massive star
Iron core collapses and triggers supernova explosion
Atomic NucleusProton
Neutron
0 50 100 150 200 250m a ss num b e r
0.0
0.2
0.4
0.6
0.8
1.0nu
mb
er f
rac
tion
Observed Nuclei in the Universe:
Hydrogen:
Mass number = 1
Helium:
Mass number = 4
91.0%
8.9%
What is the universe made of?
Iron ?
What is the Universe made of?
0 50 100 150 200 250m a ss num b e r
10-13
10-12
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
num
be
r fra
ctio
nGold:
79 protons + 118 neutrons
Mass number = 197
Iron:
26 protons + 30 neutrons
Mass number = 56
04
8
12
16 2024 28
3236
4044
4852
56 6064
6872
7680
84
8892
96100
104108
112116
120124
128 132136
140
02
46
810
1214
1618
2022
2426
2830
3234
3638
4042
4446
4850
5254
5658
6062
6466
6870
7274
7678
8082
8486
8890
92
The o rig in o f g o ld - the p a th o f nuc le o synthe sis
Gold (197Au)
HeliumHydrogen
num
ber
of p
roto
ns
number of neutrons
197Au: Au has 79 protons 197Au has 197 – 79 = 118 neutrons
04
8
12
16 2024 28
3236
4044
4852
56 6064
6872
7680
84
8892
96100
104108
112116
120124
128 132136
140
02
46
810
1214
1618
2022
2426
2830
3234
3638
4042
4446
4850
5254
5658
6062
6466
6870
7274
7678
8082
8486
8890
92
The o rig in o f g o ld - the p a th o f nuc le o synthe sis
Gold (197Au)
HeliumHydrogen
num
ber
of p
roto
ns
number of neutrons
197Au: Au has 79 protons 197Au has 197 – 79 = 118 neutrons
So how is gold made ?Some earlier failed attempts (1590)
Alchemists lab + NSCL
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)
… by Alchemy:
For example:with the “Philosopher’s Stone”
Making gold/silver from base metals
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)
04
8
12
16 2024 28
3236
4044
4852
56 6064
6872
7680
84
8892
96100
104108
112116
120124
128 132136
140
02
46
810
1214
1618
2022
2426
2830
3234
3638
4042
4446
4850
5254
5658
6062
6466
6870
7274
7678
8082
8486
8890
92
The o rig in o f g o ld - the p a th o f nuc le o synthe sis
Gold (197Au)
HeliumHydrogen
num
ber
of p
roto
ns
number of neutrons
197Au: Au has 79 protons 197Au has 197 – 79 = 118 neutrons
?
