GOALS AND OBJECTIVES
BY THE END OF THIS LESSON YOU SHOULD BE ABLE TO SAY “I CAN…”
• DESCRIBE HOW ENERGY FROM THE SUN IS CREATED.
• EXPLAIN HOW ATOMS REACT DURING THE PROCESS OF NUCLEAR FUSION IN THE SUN.
• EXPLAIN WHAT A PHOTON IS, HOW IT IS MADE, AND WHY IT’S IMPORTANT TO OUR EARTH.
HOW BIG IS THE
SUN COMPARED
TO EARTH?
The Sun and planets are shown to the
same scale. The small terrestrial planets
and tiny Pluto are in the box - the Earth is
the blue dot near the center of the box
(montage created by Nick Strobel using
NASA images).
Image copied from Nick Strobel's Astronomy Notes
STARS (LIKE THE SUN) SHINE BECAUSE OF
NUCLEAR FUSION REACTIONS IN THEIR CORE.
THE MORE LUMINOUS THEY ARE, THE MORE
REACTIONS ARE TAKING PLACE IN THEIR
CORES.
WE’RE GOING TO MAKE SOME REACTIONS OF
OUR OWN…
NASA/JPL-Caltech
THE POPCORN EXPERIMENT
OBSERVE, TAKE NOTES, MAKE CONNECTIONS AS SCIENCE CREATES A TASTY SNACK.
YOUR RESPONSE TO THE POPCORN
EXPERIMENT
Group discussion:
What did you notice about the popcorn machine?
What happened as the popcorn popped?
What made the popcorn pop?
Was it loud or quiet? (is this a form of energy?)
Was the weight of the popcorn kernels the same after they popped? Why?
WEIGHT OF POPCORN
• POPCORN KERNEL WEIGHT BEFORE POPPING: ___________________
• POPCORN WEIGHT POST POPPING:
____________________
• DIFFERENCE: ________________
WHAT IS THE SUN MADE OF?
ATOMS
Neutrons making up part of
the nucleus.
Different combinations of
protons, neutrons, and
electrons make different
atoms.
Electrons orbiting
the nucleus.
Protons making up
part of the nucleus.
ATOMS IN THE SUN…
94% Hydrogen
1 proton.
1 electron.
Note: When dealing with
NUCLEAR fusion,
we focus on the NUCLEUS of
the atom.
6% Helium
2 protons, 2
neutrons, 2
electrons.
.13% of Sun is made up of oxygen, carbon, iron, and other elements.
WHAT IS NEEDED FOR NUCLEAR FUSION?
WHAT DID THE POPCORN NEED TO POP?
WHAT DO YOU THINK ATOMS NEED TO FUSE?
THE SUN'S CORE IS ABOUT 16 MILLION K AND HAS A
DENSITY AROUND 160 TIMES THE DENSITY OF
WATER.
NORMALLY LIKE CHARGES REPEL LIKE CHARGES (THINK OF A MAGNET):
But at very high temperatures and with very strong gravitational force,
the motions of protons are high enough to overcome the forces that keep
them apart and the nucleus can fuse.
STEP 1 IN THE FUSION CHAIN REACTION:
AS PROTONS FUSE…
ONE OF THE PROTONS BECOMES A
NEUTRON AND
THIS ATOM IS NOW CALLED:
DEUTERIUM
During the process of fusion, energy is released in the form of two photons (gamma-rays).
PHOTONS
Photons (or light
particles) are basically
envelopes or packets of
energy. Energy from the
Sun travels to the Earth
as photons in a process
called radiation.
STEP 2 IN THE CHAIN REACTION
Deuterium then fuses with
another proton (now its
called tritium).
THIS FUSION AGAIN RESULTS IN
ANOTHER TWO PHOTONS
(GAMMA-RAYS) BEING CREATED.
STEP 3 IN CHAIN REACTION
TWO TRITIUM ATOMS COLLIDE AND CREATE A HELIUM ATOM.
tritium
tritium
helium
Bye! We’re
off to start
more chain
reactions.
THE KERNELS EVENTUALLY STOP POPPING…
• HYDROGEN IN THE SUN IS FUELING THE PROCESS OF NUCLEAR FUSION.
• COMPARED TO SMALLER STARS, IS THE SUN’S RATE OF CONSUMING FUEL MUCH GREATER?
• WHAT WILL HAPPEN ONCE ALL THE HYDROGEN IN THE SUN IS USED UP?
RECAP OBJECTIVES
• NUCLEAR FUSION CONVERTED THE NUCLEUS OF FOUR HYDROGEN ATOMS (PROTONS) INTO ONE HELIUM ATOM
WITH THE RELEASE OF SEVERAL PHOTONS.
• ALL THE PHOTONS ARE SCATTERED MANY, MANY TIMES AS THEY LEAVE THE STELLAR CORE. THE PHOTONS
CONVERT INTO DIFFERENT TYPES OF LIGHT AND THERMAL ENERGY.
• PHOTONS ARE THE FUNDAMENTAL PARTICLE OF LIGHT. THEY ARE PACKETS OF ENERGY FROM THE SUN.
• RADIATION, THE PROCESS OF EMITTING RADIANT ENERGY IN THE FORM OF WAVES OR PARTICLES, CARRIES
THAT ENERGY TO OUR EARTH.
Can you explain the atomic
reactions that occur in nuclear
fusion?
Can you explain what a photon is
and how it is made?
How does this impact life on
Earth?