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

?