Transcript Creation of the Chemical Elements

Creation the Element Carbon
for BI105 or how the
elemental composition of the
Universe got to be
By Dr. Harold Williams
of Montgomery College Planetarium
http://montgomerycollege.edu/Departments/planet/
Some Physics First
There are four fundamental forces in the
universe
1 GRAVITY
2 ELECTROMAGNETISM
3 WEAK NUCLEAR FORCE
4 STRONG NUCLEAR FORCE
Gravity
• Gravity which is the weakest and acts on all
mass and energy
• It acts on everything and is always attractive,
it sucks never pushes always pulls things
together.
• The largest structures from mountains to
planets to stars to galaxies to clusters of
galaxies to super clusters of galaxies are
formed by gravity.
• Gravitational forces fall off inversely
proportional to the distance squared.
• Gravitational forces are proportional to mass
energy.
Gravity
• It has not been made into a good quantum
theory yet.
• Newton’s Universal theory of gravity works
well, but has been superseded by the
General Theory of Relativity.
• General Relativity is the theory of gravity
discovered or invented by Albert Einstein in
1915. Its details are much more complicated
than electromagnetism.
Electromagnetism
• Electromagnetism is much stronger than
gravity, but only effects charges.
• Benjamin Franklin discovered that like
charges, q, repel each other and unlike
charges attract. This is the most important
fact of electromagnetism.
• When charges accelerate or decelerate
photons are emitted or absorbed.
• Photons can be radio waves, TV waves,
microwaves, infrared, visible light, ultraviolet,
x-rays, or gamma rays.
• The only difference is frequency of the wave
and energy per photon.
All Photons travel at the speed
of light, c!
• The speed of light is finite and it is the fastest
speed in the universe.
• Therefore the speed of light is the same
relative to all reference frames.
• Space and time are different; just as where
and when are different, but they are intimately
linked.
• Different observers will not agree on lengths
of objects and time intervals between events.
• Simultaneity is very tricky!
Electromagnetism
• Charges create electrical fields, E
• Moving charges, q, traveling at velocity, v,
create a magnetic field, B, and moving
charges are effected by magnetic fields.
• Magnetism is weaker than Electric and is
caused by the finite nature of the speed of
light.
• The speed of light has to be finite or we
would not live in a causal universe. There
would be not cause and effect!!!!!
Electromagnetism
• Causes chemistry, holds negatively charged
electrons, e-, around around positively
charged nuclei. Positively charge nuclei
contains protons, p+.
• Atoms, molecules, material strength, and you
are held together by electrical forces.
• Electrical forces fall off inversely proportional
to the distance squared.
Weak Nuclear Force
• Very short range, not long range like
gravity and electromagnetism.
• Causes nuclear decay, a neutrino, is
emitted.
• This causes the core of the earth to be
hot and only up and down quarks to be
stable.
Strong Nuclear Force
• Also a short range force, not long range
like gravity and electromagenistm.
• It is a much stronger force and its range
while short is longer than the weak
nuclear force.
• It hold protons and neutrons together in
the nucleus of an atom.
• It operates over nuclear distances.
Four known forces
in universe:
Strong Force
Electromagnetism
Weak Force
Gravity
Do forces unify at high temperatures?
Four known forces
in universe:
Strong Force
Electromagnetism
Weak Force
Gravity
Do forces unify at high temperatures?
Four known forces
in universe:
Strong Force
Electromagnetism
Weak Force
Gravity
Yes!
(Electroweak)
Do forces unify at high temperatures?
Four known forces
in universe:
Strong Force
Electromagnetism
Weak Force
Gravity
Yes!
(Electroweak)
Maybe
(GUT)
Do forces unify at high temperatures?
Four known forces
in universe:
Strong Force
Electromagnetism
Weak Force
Gravity
Yes!
(Electroweak)
Maybe
(GUT)
Who knows?
(String Theory)
What is the history of the
universe according to the Big
Bang theory?
Planck Era
Before Planck
time (~10-43
sec)
No theory of
quantum
gravity, yet!
GUT Era
Lasts from
Planck time
(~10-43 sec) to
end of GUT
force (~10-38
sec)
Electroweak
Era
Lasts from end
of GUT force
(~10-38 sec) to
end of
electroweak
force (~10-10
sec)
Particle Era
Amounts of
matter and
antimatter
nearly equal
(Roughly 1
extra proton
for every 109
protonantiproton
pairs!)
Era of Nucleosynthesis
Begins when
matter
annihilates
remaining
antimatter at
~ 0.001 sec
Nuclei begin to
fuse
Era of Nuclei
Helium nuclei
form at age
~ 3 minutes
Universe has
become too
cool to blast
helium apart
Protons and neutrons combined to make long-lasting helium
nuclei when universe was ~ 3 minutes old
Big Bang theory prediction: 75% H, 25% He (by mass)
Matches observations of nearly primordial gases
Abundances of
other light
elements agree
with Big Bang
model having
4.4% normal
matter – more
evidence for
WIMPS!
Era of Atoms
Atoms form at
age ~ 380,000
years
Background
radiation
released
The cosmic
microwave
background –
the radiation left
over from the
Big Bang – was
detected by
Penzias &
Wilson in 1965
Background radiation from Big Bang has been freely
streaming across universe since atoms formed at
temperature ~ 3,000 K: visible/IR
Background has perfect
thermal radiation
spectrum at temperature
2.73 K
Expansion of universe has redshifted thermal
radiation from that time to ~1000 times longer
wavelength: microwaves
Around 380,000 years after
the Beginning of Time
Era of
Galaxies
Galaxies form
at age ~ 1
billion years
Star form
earlier ending
the dark ages
~200 million
years.
So after the Big Bang the
Universe is Composed Of
•
•
•
•
75% by weight Hydrogen, 1H
25% by weight Helium, 4He
A small amount of Deuterium, 2H
An even smaller amount of Lithium and
Beryllium, Li and Be and some 3He.
• No Carbon, C, no Nitrogen, N, no
Oxygen, O, no heavy elements like Iron,
Fe, or Magnesium, Mg, Sulfur, S, or
Potassium, K, or Phosphorus, P.
Elemental Composition of the
Universe the song lyrics by
Harold and Barbara Williams
•
•
•
•
•
•
Twinkle, Twinkle, little star.
Yes I know just what you are.
You’re three quarters hydrogen,
and one quarter helium
with trace amounts of other things
from pink sea shells, to diamond rings.
How do high-mass stars make
the elements necessary for
life?
http://en.wikipedia.org/wiki/Triple-alpha_process
http://en.wikipedia.org/wiki/Neon_burning_process
http://en.wikipedia.org/wiki/Silicon_burning_process
CNO Cycle
http://en.wikipedia.org/wiki/CNO_cycle
• High-mass main
sequence stars fuse
H to He at a higher
rate using carbon,
nitrogen, and oxygen
as catalysts
• Greater core
temperature enables
H nuclei to overcome
greater repulsion
Big Bang made 75% H, 25% He – stars make everything else
Helium fusion can make carbon in low-mass stars
CNO cycle can change C into N and O
Helium Capture
•
High core temperatures allow helium to
fuse with heavier elements
Helium capture builds C into O, Ne, Mg, …
Advanced Nuclear Burning
•
Core temperatures in stars with >8MSun
allow fusion of elements as heavy as
iron
Advanced reactions in stars make elements like Si, S, Ca, Fe
Multiple Shell Burning
• Advanced nuclear
burning proceeds
in a series of
nested shells
Iron is dead
end for fusion
because nuclear
reactions
involving iron
do not release
energy
(Fe has lowest
mass per
nuclear
particle)
Evidence for
helium
capture:
Higher
abundances of
elements with
even numbers
of protons
Iron builds up
in core until
degeneracy
pressure can no
longer resist
gravity
Core then
suddenly
collapses,
creating
supernova
explosion
How does a high-mass star
die?
Supernova Explosion
http://en.wikipedia.org/wiki/Supernova
• Core degeneracy pressure
goes away because electrons
combine with protons,
making neutrons and
neutrinos
• Neutrons collapse to the
center, forming a neutron
star
• http://en.wikipedia.org/wiki
/Neutron_star
Energy and neutrons released in supernova explosion enable elements
heavier than iron to form, including Au and U
Supernova Remnant
http://en.wikipedia.org/wiki/Crab_nebula
• Energy released by
collapse of core
drives outer layers
into space
• The Crab Nebula is
the remnant of the
supernova seen in
A.D. 1054, M1, NGC
1952, Taurus A,
~6,300LY away, 3LY
radius, optical and
radio pulsar
Supernova 1987A
http://en.wikipedia.org/wiki/Supernova_1987a
•
The closest supernova in the last four
centuries was seen in 1987
Rings around Supernova
1987A
•
The supernova’s flash of light caused
rings of gas around the supernova to
glow
Impact of Debris with Rings
•
More recent observations are showing
the inner ring light up as debris
crashes into it