Download The Universe Inside of You: Where do the atoms in your body come

The Universe Inside of You:
Where do the atoms in your body come from?
Matthew Mumpower
University of Notre Dame
Thursday June 27th 2013
Nucleosynthesis
nu·cle·o·syn·the·sis The formation of new atomic nuclei by nuclear reactions, thought
to occur in the interiors of stars and in the early stages of development of the universe.
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Nuclear Physics
Astrophysics
“We are all made of star stuff...”
Nuclear Physics Tells Us
How nuclei transmute (how one nucleus is turned into another via nuclear reactions)
And the energy associated with these various processes.
Nuclear reactions are the fuel for stars...
Creation of new elements is an energy source of stars (and the sun)
Astrophysics Tells Us
The properties celestial objects as well as their interactions and time evolution.
Stellar Burning
Stellar Evolution
Our Sun
Shines 3.85*1033 erg/s ~ 3.85*1026 Watts for ~4.5 billion years.
The sun in x-rays
A sun made of coal would only last ~4000 years.
Our Sun
Shines 3.85*1033 erg/s ~ 3.85*1026 Watts for ~4.5 billion years.
The sun in x-rays
A sun made of coal would only last ~4000 years.
“Billions and billions...”
How Old Are The Atoms on Earth?
Solar System formed ~4.6 billion years ago from gravitational collapse of interstellar
dust cloud.
This cloud was generated from previous supernova explosions.
Most atoms on Earth are > 4.6 billion years old.
Artist's concept of protoplanetary disk
“Stuff” In the Solar System
Abundance is a quantity denoting how much stuff
Heavier elements
More stuff
Less stuff
(number of protons)
We know the amount of stuff in the Solar System because we have data from
meteorites and the sun's photosphere (outer shell). The sun has 99% of the mass of
the solar system – so it is important to understand its composition.
“Stuff” In the Solar System
Iron
Gold
A ~ 56
A ~ 197
More stuff
Less stuff
(number of protons)
Creation of the elements did not occur all at the same time nor same place
This requires some detective work...
What Is The Origin Of The Elements?
Lightest Elements: Big Bang
Big Bang Nucleosynthesis
Created most of the Hydrogen and Helium in the universe.
Started within the first 3 minutes of the beginning of the universe.
Ended within about 20 minutes due to expanding and cooling.
Only ~12 key reactions to take into account!
“If you wish to make an apple pie from
scratch, you must first invent the universe. ”
Cosmic Rays
Stellar Burning Processes
Stellar Burning Processes
Nuclear Fuel Main Products
H
He
He
C, O
C
Ne, Mg
Ne
O, Mg
O
Si, S
Si
Fe
Coal
T (109 K) Duration (yr)
0.037
8 * 106
0.19
1 * 106
0.87
1 * 103
1.6
0.60
2.0
0.25
3.3
0.03
Energy: Unfavorable Once We Reach Fe
Nuclear Fuel Main Products
H
He
He
C, O
C
Ne, Mg
Ne
O, Mg
O
Si, S
Si
Fe
T (109 K) Duration (yr)
0.037
~ 8 * 106
0.19
~ 1 * 106
0.87
~ 1 * 103
1.6
~ 0.60
2.0
~ 0.25
3.3
< 0.03
p,s,r Processes
Particle Accelerators
Synthesis of The Heavy Elements
Still many open problems...
Where are these elements synthesized? (site?)
Does fission of the heaviest elements play a role?
It is difficult to produce short-lived nuclei that can
participate in these processes.
What are the masses or half-lives of short-lived
nuclei?
Question
Question #3
#3
How
How were
were the
the elements
elements from
from
iron
iron to
to uranium
uranium made
made ??
Chart of Nuclides
This system of ordering nuclei can offer a greater insight into the characteristics of
isotopes than the better-known periodic table, which shows only elements instead of
each of their isotopes.
Gold
Stable nuclei
Known nuclei
O
No known info
Possible r-process
path
What do lines of constant A = Z + N look like?
So How Is Gold Made?
Some early attempts tried to use alchemy
Turn a base metal into gold or silver
A famous example is the philosopher's
stone (1590)
By a nuclear reaction in the lab
For example:
208
Pb + 9Be → 197Au + p + ….
Makes gold from lead… at a very slow rate
(20,000 nuclide/sec)
So How Is Gold Made?
Expose iron to a flux of neutrons
Recall: not energetically favorable to keep adding protons.
There are two possibilities:
Capture neutrons very quickly (rapid or r-process).
Capture neutrons very slowly (slow or s-process).
Neutron Capture / Photo-dissociation
Beta Decay
The s-Process
Timescale for capturing a neutron can be 10 years or longer!
Where does this process take place? - In Giant Branch stars
There !
“Path” of the nuclear
reactions stays close
to stability.
This process takes
millions of years to
reach its end point
(Bismuth-209).
But we see elements
heavier than Bi-209 →
they must be created
in the r-process
The s-Process
How do we know that nucleosynthesis is going on in red giant stars?
Merrill (1952) analyzed the light coming from a red giant and found Technetium (Tc).
Tc (Z=43) has no stable isotope (longest ~ 4 million yrs). So since it was found in the
star it had to be created there.
Another Way To Make Au: The r-Process
Capture neutrons very quickly - “rapid” compared to the time it takes to beta-decay.
So many neutrons are captured that we push the “path” far from the stable isotopes.
No information on nuclear properties of thousands of nuclei that participate in this
process because they are too short-lived to be measured.
Further complicated because we don't know the location(s) where this process occurs.
The location must be able to provide a lot of neutrons!
Event lasts ~10 seconds
Neutron Capture / Photo-dissociation
Beta Decay
One Possible r-Process Candidate Site
Supernova – End of the life of a massive star (remember the iron core?)
Extremely luminous - burst of radiation that can outshine host galaxy for several
weeks expelling most of the star's material
During this short interval a supernova can radiate as much energy as the Sun is
expected to emit over its entire life span.
Can it produce neutron rich material?...
Another Possible r-Process Candidate Site
Neutron Star Mergers – Two neutron stars come together in a violent collision
Extremely neutron rich – provides more than enough neutrons to produce the rprocess
Must understand fission of heavy nuclei in order to accurately predict r-process
abundances in this site
A simulation of two neutron stars merging and expelling material
Some Clues From Astrophysics
We look to the galactic halo and analyze the abundances of very old “halo” stars.
We find that the composition of these stars is similar to the Solar System.
This means that whatever processes are at work creating the heavy elements are
fairly universal.
Maybe It's Both?
Could supernova and neutron star mergers both be responsible for the r-process?
Look at Europium (a known r-process element) in stars.
There seems to be two components.
More r-process
material
r-Process Enrichment [Eu/Fe]
Older stars
5.0
4.0
3.0
2.0
1.0
0.0
-1.0
-6.0
-5.0
-4.0
-3.0
-2.0
Metallicity
-1.0
[Fe/H]
0.0
1.0
Data from the Stellar Abundances for Galactic Archeology (SAGA) database
A Simple r-Process Calculation
nuclear physics inputs
(Sn, β-rates, n-cap rates, … )
reaction network
Environment conditions
(temperature, density, ... )
abundances
Other Nucleosynthesis Processes
How to make the proton-rich heavy elements?
Proton capture (p-process) and rapid proton capture (rp-process)
Other astrophysical environments? More investigation needed...
More movies of nucleosynthesis: http://www.jinaweb.org/html/gallery_scimovies.html
Summary
●
Carl Sagan has some good quotes
●
Solar system is about 4.5 billion years old
●
Sun will “live” for another ~5 billion years
●
“Heavy” Elements are created by stars
●
●
●
Different processes occur in different
sites and produce different isotopes
Nuclear physics is import to
understanding abundances
Window of a church in Wixhausen, Germany
Even German churches like
nucleosynthesis
“... and billions...”