Nuclear Astrophysics
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Nuclear Astrophysics. by Richard Cyburt. 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.

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Nuclear Astrophysics

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Nuclear astrophysics

Nuclear Astrophysics

by Richard Cyburt


Nuclear astrophysics

Creation of new elements is energy source of stars (and the sun)

“We are made of star stuff….” Carl Sagan


Nuclear astrophysics

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


Nuclear astrophysics

NucleusFactories


Nuclear astrophysics

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


Nuclear astrophysics

Periodic Table of Elements in nature


Nuclear astrophysics

Elements in nature

Made in the Big Bang


Nuclear astrophysics

Elements in nature

Made by fusion in stars…


Nuclear astrophysics

Elements in nature

How are the elements heavier than iron made?


Nuclear astrophysics

Burning stages of a 25 solar mass star

initially present: mostly hydrogen (~70% - from big bang)

Hydrogen burning

Hydrogen (1p,0n)

Helium (2p, 2n)

7Mio yrs

Helium burning

Helium (2p,2n)

Carbon (6p, 6n), Oxygen (8p,8n)

700,000 yrs

Carbon(+Ne) burning

Carbon (6p,6n)

Oxygen (8p,8n)

400 yrs

Oxygen burning

Oxygen (8p,8n)

Silicon (14p,14n)

8 months

Silicon burning

Silicon (14p,14n)

Nickel (28p,28n)

1 day


Nuclear astrophysics

Average binding energy per nucleon (MeV)

For stable nuclei !!!


Nuclear astrophysics

Window of the Protestant church in Wixhausen, Germany


Nuclear astrophysics

Precollapse structure of massive star

Iron core collapses and triggers supernova explosion


Nuclear astrophysics

How to make Gold

... and the other heavy elements


Nuclear astrophysics

Atomic Nucleus

Proton

Neutron


Nuclear astrophysics

What is the universe made of?

Hydrogen:

Helium:

Mass number = 1

Mass number = 4

Observed Nuclei in the Universe:

91.0%

Iron ?

8.9%


What is the universe made of

What is the Universe made of?


Nuclear astrophysics

Iron:

Gold:

26 protons + 30 neutrons

79 protons + 118 neutrons

Mass number = 56

Mass number = 197


Nuclear astrophysics

Gold (197Au)

197Au: Au has 79 protons197Au has 197 – 79 = 118 neutrons

number of protons

Helium

number of neutrons

Hydrogen


Nuclear astrophysics

Gold (197Au)

197Au: Au has 79 protons197Au has 197 – 79 = 118 neutrons

number of protons

Helium

number of neutrons

Hydrogen


Nuclear astrophysics

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)

Alchemists lab + NSCL

… by a nuclear reactionfor example: 208Pb + 9Be -> 197Au + p + ….

Makes gold from lead…

at a very slow rate

(20,000 nuclide/sec)


Nuclear astrophysics

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


Nuclear astrophysics

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


Nuclear astrophysics

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)


Nuclear astrophysics

197Au: Au has 79 protons197Au has 197 – 79 = 118 neutrons

Gold (197Au)

number of protons

?

Helium

number of neutrons

Hydrogen


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