The document discusses how heavier elements are formed in stars through nuclear fusion reactions. It begins by outlining the key terms and concepts, including fusion, stellar nucleosynthesis, and the proton-proton chain reaction. It then explains several important nuclear fusion processes that occur in stars, such as the triple alpha process, alpha ladder, CNO cycle, and how these lead to the formation of carbon, oxygen, and heavier elements up to iron. The document also describes stages in the life of stars, from main sequence stars to red giants and supernovae, which generate even heavier elements through rapid neutron capture processes.

1. We are all made of Star stuff
(Formation of the Heavy
Elements)
Physical Science-Grade 11

2. Objectives:
1. Give evidence for and describe the formation of heavier
elements during star formation and evolution.
2. Write the nuclear fusion reactions that take place in stars,
which lead to the formation of new elements.
3. Describe how elements heavier than iron are formed.

3. Important terms:
 A. Fusion
 B. Stellar nucleosynthesis
 C. Proton-proton chain reaction
 D. Triple alpha process
nucleosynthesis
 E. Alpha ladder
 F. CNO cycle
 G. Main-sequence star
 H. Red giant
 I. Supernova explosion
 J. Supernova
 K. R-process
 L. S-process

4. Fusion

5. Fusion
refers to the process of combining or merging
two or more things together to form a single
entity.

6. Stellar nucleosynthesis


7. Stellar nucleosynthesis
 is the process by which elements are formed in
stars through nuclear reactions.

8. Proton-proton chain reaction

9. Proton-proton chain reaction
 is a series of nuclear reactions that occur in the
core of the Sun and other stars to produce
energy.

10. Triple alpha process nucleosynthesis

11. Triple alpha process nucleosynthesis
 is a nuclear reaction that plays a crucial role in the
nucleosynthesis of elements in the universe. It involves
the fusion of three helium-4 nuclei (alpha particles) to
form carbon-12.

12. Alpha ladder

13. Alpha ladder
 is one of two classes of nuclear fusion reactions by
which stars convert helium into heavier elements.

14. CNO cycle

15. CNO cycle
 is one of the two known sets of fusion reactions by
which stars convert hydrogen to helium, the other
being the proton–proton chain reaction (p–p cycle),
which is more efficient at the Sun's core temperature.

16. Main-sequence star

17. Main-sequence star
Main sequence stars are a stage in the life cycle
of a star. They are stars that are fusing hydrogen
into helium in their cores, which produces the
energy that makes them shine.

18. Red giant

19. Red giant
Red giants are evolved stars that have exhausted
the supply of hydrogen in their cores and instead
burn hydrogen in a surrounding shell. They are in
the late stages of stellar evolution.

20. Supernova explosion

21. Supernova explosion
A supernova explosion is a powerful event
that occurs at the end of a star's life. It is a
catastrophic event that releases an
enormous amount of energy and results in
the ejection of the star's outer layers into
space.

22. Supernova

23. Supernova
are powerful explosions that occur at the end of
a star's life. They release an enormous amount of
energy and can shape galaxies.

24. R-process

25. R-process
The r-process, or rapid neutron capture process, is a nuclear
reaction that occurs in extreme astrophysical environments,
such as supernovae or neutron star mergers. During the r-
process, heavy elements beyond iron are formed through the
rapid capture of neutrons by atomic nuclei. This process is
responsible for the creation of approximately half of the
elements heavier than iron in the universe.

26. S-process

27. S-process
The s-process, or slow neutron capture process, is a
nucleosynthesis process that occurs in stars. It is
responsible for the production of elements heavier than
iron in the periodic table. During the s-process, atomic
nuclei capture slow-moving neutrons, which then
undergo beta decay, resulting in the formation of
heavier elements.

28. Let’s review the stages of the Big Bang model

30. Carl Sagan’s Cosmic
Connection

31. Assignment last time:
Read in advanced about carl Sagan’s The cosmic connection
and answer the following questions:
1. Astrology and astronomy both deal with the stars and planets. List at
least three differences between them.
2. Why did human invent astrology? How do we know astrology is not a
real study?
3. Give your idea that science say we are connected with the universe.
4. Carl Sagan famously says “We are made of star stuff.” What do you
think he meant by that?

32. Astrology vs. Astronomy
Astronomy is the branch of science that
studies everything outside of Earth's
atmosphere.
Astrology is the nonscientific practice of
using the positions of celestial objects to
explain or predict human behavior.

33. Astronomy
1. study of everything outside of the earth's atmosphere (celestial
bodies like the planets, stars, asteroids, galaxies etc.) or simply the
study of the universe
2. Astronomers base their study through observation and research.
3. a natural science
Astrology
1. study on how the positions, motions and properties affect the way
events happen on Earth and the life of each individual (horoscopes)
2. Astrologers base their study through belief and superstitions (they
don't look through telescopes and learn about the celestial objects
like the astronomers do) and do not follow the scientific method
(research).
3. a pseudo-science (a collection of beliefs or practices mistakenly regarded as
being based on scientific method.)

34. Carl Sagan’s Cosmic Connection
Sagan found it remarkable that the elements we find on
Earth are also those we find among the stars. In
addition, we find that most of what we know as matter
was made by processes inside stars themselves.

35. Think and share with your seatmate:
We are as much a part of the universe as the stars.
Discuss how being made of stardust makes us cosmic
and yet helps us realize that we are not the center of
the universe.

36. How did
hydrogen and
helium atoms
in stars began
combining in
nuclear fusion?

37. How did hydrogen and helium atoms in stars
began combining in nuclear fusion?
Hydrogen and helium atoms in stars began combining in
nuclear fusion reactions once hydrogen-helium stars had
formed from the action of gravity. This releases a tremendous
amount of light, heat, and radioactive energy. Fusion resulted in
the formation of nuclei of new elements.

38. How did hydrogen and helium atoms in stars
began combining in nuclear fusion?
Nuclear fusion is the process by which two light
atomic nuclei combine to form a single heavier
one while releasing massive amounts of energy.

39. What is the result of fusion?
Fusion resulted in the formation of nuclei of
new elements. These reactions inside stars
are known as stellar nucleosynthesis.

40. Let’s watch a video about the life of a star.

42. Evolution of Stars
stars form due to the collapse of the dense regions of
a molecular cloud. As the cloud collapses, the
fragments contract to form a stellar core
called protostar. Due to strong gravitational force, the
protostar contracts and its temperature increases.
When the core temperature reaches about 10 million
K, nuclear reactions begin. The reactions release
positrons and neutrinos which increase pressure and
stop the contraction. When the contraction stops, the
gravitational equilibrium is reached, and the protostar
has become a main sequence star.


43. In the core of a main sequence star, hydrogen is fused into
helium via the proton-proton chain. When most of the
hydrogen in the core is fused into helium, fusion stops, and
the pressure in the core decreases. Gravity squeezes the
star to a point that helium and hydrogen burning occur.
Helium is converted to carbon in the core while hydrogen
is converted to helium in the shell surrounding the core.
The star has become a red giant.

44. The first fusion process occurs in the hydrogen core of
stars such as the sun with a temperature of less than 15
million Kelvin. These kinds of stars are called main-
sequence stars.

47. Let’s discuss:
Proton-proton chain
Red giant
Alpha ladder
CNO cycle

48. Proton-proton chain
 First, two hydrogen nuclei (1H) combine to form a hydrogen-2
nucleus (2H, deuterium) with the emission of a positive electron (e+,
positron) and a neutrino (ν)(a neutral subatomic particle with a mass
close to zero, rarely reacting with normal matter). The hydrogen-2
nucleus then rapidly captures another proton to form a helium-3
nucleus (3He), while emitting a gamma ray (γ). In symbols:
Chemical equations.

51. Red giant
When the core of a star becomes compromised of He as H is
depleted, while H fusion only occurs in a shell around it the
temperature and density of the core of the star increases up to
100 million K. The star’s thermal pressure causes it to push out
of H gas. The star balloons into a red giant. Several nuclear
fusion processes occur in a red giant aside from hydrogen
fusion. The first is the triple alpha process. Alpha particles refer
to 4He. This reaction involves the fusion of three 4He atoms.

54. Alpha ladder
The star can keep growing into a supergiant as it accumulates
mass. Alpha fusion processes continue in the core via the alpha
ladder. More and more alpha particles are fused to create
heavier elements all the way to iron, making the core and star
itself more massive.

56. CNO Cycle
The main sequence stars hotter than 15 million K could facilitate
the production of helium once carbon was present from alpha
processes. This happens through a process where 12C is used
as a catalyst known as the carbon fusion cycle or the CNO cycle.

57.  CNO CYCLE
The ‘CNO cycle’ refers to the Carbon-Nitrogen-Oxygen cycle, a process of stellar
nucleosynthesis in which stars on the Main Sequence
fuse hydrogen into helium via a six-stage sequence of reactions. This sequence
proceeds as follows:
-A carbon-12 nucleus captures a proton and emits a gamma ray, producing
nitrogen-13.
-Nitrogen-13 is unstable and emits a beta particle, decaying to carbon-13.
-Carbon-13 captures a proton and becomes nitrogen-14 via emission of a
gamma-ray.
-Nitrogen-14 captures another proton and becomes oxygen-15 by emitting a
gamma-ray.
-Oxygen-15 becomes nitrogen-15 via beta decay.
-Nitrogen-15 captures a proton and produces a helium nucleus (alpha particle)
and carbon-12, which is where the cycle started.

60. Supernova- is the biggest explosion that humans have
ever seen. Each blast is extremely bright, super-powerful
explosion of a star.
 Finally, a star will eventually be unable to generate energy to push against
gravity due to the formation of heavier elements, thus causing it to
collapse on itself. It then undergoes a supernova explosion that releases
tremendous amount of energy enough to synthesize elements heavier
than iron. Examples of these elements are uranium and thorium, which are
some of the heaviest known elements. This is done through the r-process
that involves rapid capture of neutrons by the atom. Other heavy elements
are also synthesized through s-process involving slow neutron capture in
red giants.

62. Practice:
Write all the equations involved in the alpha
ladder using the periodic table. What have you
noticed about the atomic number patterns of the
elements found in the ladder.

63. Performance Task:
 Quite a few elements were first discovered as man-made elements
since many of them did not emerge from the major nucleosynthesis
reactions. These include elements Americium through Lawrencium, as
well as some of the recently discovered elements like Flerovium and
Livermorium. Research on one of these elements.
 1. discuss the element’s basic characteristics.
 2. Give a brief timeline leading up to element’s discovery.
 3. You may present in the form of a poster, power point, essay, video, or
infographic.

65. Evaluation