2. Physical Science β Grade 11
Quarter 3 β Module 1: Star Formation and Evolution
First Edition, 2020
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Development Team of the Module
Writer: Jovanni P. Tubal
Editor: -
Reviewer: Faye Genevieve P. Pasamonte, Genevaive M. Pepito
Illustrator: Reden S. Ranalan
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Jinky B. Firman
Marilyn V. Deduyo
Alma C. Cifra
Aris B. Juanillo
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4. ii
Introductory Message
For the facilitator:
As a facilitator, you are expected to orient the learners on how to use this
module. You also need to keep track of the learners' progress while allowing them to
manage their own learning at home. Furthermore, you are expected to encourage
and assist the learners as they do the tasks included in the module.
For the learner:
As a learner, you must learn to become responsible of your own learning. Take
time to read, understand, and perform the different activities in the module.
As you go through the different activities of this module be reminded of the
following:
1. Use the module with care. Do not put unnecessary mark/s on any part of the
module. Use a separate sheet of paper in answering the exercises.
2. Donβt forget to answer Let Us Try before moving on to the other activities.
3. Read the instructions carefully before doing each task.
4. Observe honesty and integrity in doing the tasks and checking your answers.
5. Finish the task at hand before proceeding to the next.
6. Return this module to your teacher/facilitator once you are done.
If you encounter any difficulty in answering the tasks in this module, do not
hesitate to consult your teacher or facilitator. Always bear in mind that you are not
alone. We hope that through this material, you will experience meaningful learning
and gain deep understanding of the relevant competencies. You can do it!
5. 1
Let Us Learn
This module was designed for you, the learners. It is to facilitate you to learn
the appropriate knowledge and skills as you go through a series of worthwhile
activities. The lessons are arranged sequentially in this course to ease understanding
and mastery. The parameter of this module allows you to appreciate the formation
of heavier elements in the universe through star formation and evolution and the
pieces of evidence.
After going through this module, you are expected to:
β’ Give evidence for and describe the formation of heavier elements during
star formation and evolution (MELC).
Specifically, you will:
1. identify the heavier elements formed in the star evolution and their
atomic masses
2. explain the formation of heavier elements in the stages of star
evolution; and,
3. cite evidence about the formation of heavier elements during star
formation and evolution.
Let Us Try!
Choose the best answer and write your answers on a separate paper.
1. Where is the site of the formation of heavier elements in the universe?
A. Asteroid Belt C. Moon
B. Earth D. Star
2. Which of the following is the correct sequence of the evolution of the star?
A. main sequence star, supergiant, red giant, supernova
B. red giant, supergiant, main sequence star, supernova
C. main sequence star, red giant, supergiant, supernova
D. supernova, main sequence star, red giant, supergiant
6. 2
3. What happens to the core temperature of a star as it ages/ evolves?
A. Decreases
B. Increases
C. Remains constant
D. Increases then decreases
4. In the main sequence star, what element is formed when hydrogen fuse in
the starβs core?
A. Beryllium C. Helium
B. Carbon D. Oxygen
5. How is the heavy element Carbon formed in a starβs core? It is formed via:
A. Explosion of the star C. Hydrogen Fusion
B. Helium Fusion D. Oxygen Fusion
Let Us Study
Have you observed the bright stars in a clear night sky? Have you witnessed
the spectacular sunrise at dawn? I think you have. The sun is also a star in the
universe. Both the stars and sun in the universe take part of our everyday lives. We
could even say that we are the universeβs way of experiencing itself.
Meanwhile, looking beyond what we see in our own two eyes spark more the
inquisitive mind.
What are stars made of? How are they formed? Would they stay up in the sky
infinitely throughout their lifetime? These are just some of the queries that will be
unraveled in detail in this module.
Read the comic strips below and answer the questions that follow:
7. 3
Questions:
1. What is the most abundant element in the Universe?
2. What do you call the process in which heavier elements (e.g. lithium and
beryllium) are formed?
3. Where do formation of heavier elements take place?
What is a Star?
A star is a ball of gas strongly held together by its own gravitational force. The
Sun, our very own star, is the closest star to Earth and has been used by astronomers
as a model in studying stars in detail.
A starβs life starts as clouds of dust and gas. Gravity pulls these clouds
together. Various nuclear fusion reactions take place and drive the formation and
development of stars. Stars with different masses grow and βevolveβ (or change)
throughout the different stages of their lives.
Stars, in general, begin life in the same way however they develop in different
ways depending on their size.
The sun, our star, is formed around 4.5 billion years ago. It is driven by
nuclear fusion, initially involving hydrogen and producing helium along with a high
amount of energy. This is the source of the energy of a star like our sun.
How Are Stars Formed?
Oh really! I donβt
know that. Thank
you, Hannah!
Andres, do you
know that
Hydrogen is the
most abundant
element in the
universe?
I am learning
a lot from
you, Hannah.
In fact, hydrogen,
together w/ helium,
lithium & beryllium,
were formed through Big
Bang nucleosynthesis.
How about
the formation
of heavier
elements?
Interestingly, they
were formed within
stars.
That sounds
cool! I want to
know more of
thatβ¦
Comic Strip By: Reden S. Ranalan
8. 4
The outer space may seem like a vacuum but in reality, it contains very thinly
spread of gas and dust called the interstellar medium (ISM). Stars are formed from
the accumulation (or accretion) of these clouds of dust and gas, referred to as
molecular clouds. The gravitational energy pulls together the clouds of gas and
dust causing it to collapse. As the clouds of gas and dust collapse, they become
denser and this paves the way for the formation of stars. The dense clouds of gas
and dust are known as a nebula β the birthplace of stars. The Orion Nebula situated
in our galaxy, the Milky Way, is one of the brightest nebulae that can be observed in
the night sky.
The formation of stars involves several stages and each stage could take
around million years.
The process of star formation
The figure on the process of star formation shows the six (6) steps (A to F) of
star formation for Sun-like stars. The process begins on (A), where clouds of gas and
dust in the space between stars (ISM) collapse into a dense sphere of gas called a
prestellar core (B) that eventually will become the sun.
During the collapse, a disk (C) forms around the core, while two jets are
emitted at the poles. At some point the star stops growing, but gas still fall onto the
disk (D). After a few million years this process also halts. The star is now born (E),
while the planets are being formed from the left-over material, which will eventually
become a solar system (F). A solar system typically lives 10 billion years after the
formation process.
9. 5
Stars spend the majority of their life fusing hydrogen into helium through a
process called nuclear fusion. When the hydrogen is nearly used up, the star can
fuse helium into heavier elements. Elements heavier than beryllium are formed
inside the stars known as stellar nucleosynthesis.
The star formation theory suggests that stars are formed from the collapse
of the dense sections of molecular cloud. As this cloud collapses, the fragments
shrink to form a stellar core known as protostar. The protostar shrinks due to strong
gravitational force while its temperature increases. When the core temperature
reaches about 10 million Kelvin, nuclear reactions start. As a result, the contraction
is stopped and gravitational equilibrium is attained. The protostar has become a
main sequence star.
Evolution of Stars
The figure below shows the life cycles of stars:
Stars that are similar in size to the Sun follow the lower path in the figure:
β’ Red giant star β white dwarf β black dwarf
Stars that are far greater in mass than the Sun follow the upper path in the figure:
β’ red super giant star β supernova β neutron star, or a black hole
(depending on size)
10. 6
Table 1. Evolution of Stars
Stage
Core
Temperature
Description Reaction
Main-sequence
star (yellow
star)
1.5 x 107 K In this stage, nuclear fusion of
hydrogen occurs in the core
that convert hydrogen into
helium. Four hydrogen atoms
combine to make a helium
atom and high energy gamma
rays. This hydrogen fusion
occurs in three steps.
Due to this process, the
temperature and density of
the starβs core increases up to
100 million K. As such, the
star expands into a red giant.
1H + 1H = 2H + Ξ²
2H + 1H = 3He + Ξ³
3He + 3He = 4He + 2
1H
Element Formed:
Helium (He)
Red giant 2 x 108 K In this stage, several nuclear
fusion reactions take place. It
involves alpha particles ( He
2
4
)
and fusion of three He
2
4
atoms.
Helium is converted to carbon
in the core while hydrogen is
converted to helium in the
shell surrounding the core.
Then, the rate of fusion slows
down. Gravity again squeezes
the star. Hence, the star
balloons into a supergiant as
it accumulates mass and
temperature.
He
2
4
+ He
2
4
= Be
4
8
Be
4
8
+ He
2
4
= C
6
12
+ Ξ³
Element Formed:
Carbon (C)
Note:
Symbol
Alpha (Ξ±) He
2
4
Beta (Ξ²) π
β1
0
Gamma (Ξ³) π
0
0
11. 7
Supergiant 7 x 108 K In this stage, carbon fusion
occurs. The star undergoes a
series of reaction as more
alpha particles are fused to
form heavier elements all the
way to iron in the core and in
the shells around the core.
The element oxygen is formed
from carbon fusion; neon from
oxygen fusion; magnesium
from neon fusion; silicon from
magnesium fusion until iron
is formed. This process makes
the core and star itself more
massive.
C
6
12
+ He
2
4
O
8
16
O
8
16
+ He
2
4
Ne
10
20
Ne
10
20
+ He
2
4
Mg
12
24
Mg
12
24
+ He
2
4
Si
14
28
Si
14
28
+ He
2
4
S
16
32
S
16
32
+ He
2
4
Ar
18
36
Ar
18
36
+ He
2
4
Ca
20
40
Ca
20
40
+ He
2
4
Ti
22
44
Ti
22
44
+ He
2
4
Cr
24
48
Cr
24
48
+ He
2
4
Fe
26
52
Elements Formed:
Oxygen (O)
Neon (Ne)
Magnesium (Mg)
Silicon (Si)
Sulfur (S)
Argon (Ar)
Calcium (Ca)
Titanium (Ti)
Chromium(Cr)
Iron (Fe)
12. 8
Supernova 1 x 1011 K Finally, in this stage the
core is eventually unable to
further generate energy to
resist gravity due to the
formation of heavier
elements. The gravity
squeezes the core until the
star explodes and releases
high amount of energy into
space enough to form
elements heavier than iron
such as thorium and
uranium, except
transuranium elements
(Refer to Periodic Table of
Elements).
Subsequently, these
elements are absorbed in
the dust that condensed to
form new stars. Such star
explosion is known as
supernova.
Elements with
atomic
mass/weight
heavier than Iron
(Fe), except
transuranium
elements.
Pieces of Evidence
1. Discovery of interstellar medium. This interstellar medium filled the
βempty spaceβ between the stars. Molecular clouds of this medium are dense regions
where the concentrations of gas and dust are thousands of times greater than
elsewhere. It has become a reservoir from which matter like stars can be formed.
Hence, it provided a major piece of evidence which supported the star formation
theory.
2. Infrared Radiation (IR). This heat energy is emitted from different stages
of star formation and evolution. Most of the new stars cannot be seen in the visible
light because dense clouds of gas block their light. But using infrared spectrum, it
reveals the young stars behind the column of gas and dust. Through this, IR has
given us keys to unlock the mystery of the universe and to explain how stars are
born and to trace the origin of galaxies.
13. 9
Let Us Practice
Activity 1: Unlocking Heavier Elements
Supply the needed information in the table below. For the third column, please
refer to the Periodic Table of Elements on page 16 as you answer. The first item is
done for you.
You may begin!
Stages Element/s Formed Atomic
mass/weight
1. main sequence star Helium (He) 4.0026
2. red giant star
3. supergiant star
4. supernova (at least 3
elements)
Processing Questions: Answer briefly. Please answer on a separate paper.
1. What do you observe to the atomic mass/weight of the elements as the star
ages/evolves?
______________________________________________________________________________
14. 10
2. How is the heavier element Carbon formed in the process?
______________________________________________________________________________
3. How are heavier elements like O, Ne, Mg, Fe and the like formed in supergiant
star?
_______________________________________________________________________________
4. What piece of evidence supports that young stars are formed from gas and dust
particles?
_______________________________________________________________________________
Were you able to accomplish it? I hope you find the task easy and challenging.
Let Us Practice More
Activity 2: Fusion Reactions
Elements are produced in the cores of high-mass stars by fusion
reactions. All stars start by burning hydrogen and end up creating many
heavier elements inside their cores. It is this kind of star that will eventually
spread the elements it created in its core when it dies in a supernova
explosion.
Your task is to complete the series of fusion reactions to show the
various reactions that create helium, carbon, magnesium, oxygen, sulfur,
neon, nickel, cobalt and the 4 different isotopes of iron. Complete the series
of reactions by supplying the missing element in the blanks with numbers 1
to 10 enclosed in parenthesis. Remember to follow the law of conservation of
mass and charge.
Hydrogen is the most abundant element in the Universe and the first element
on the periodic table. Almost 90% of the Universe is hydrogen. The second most
abundant element is helium.
Nearly 10% of the Universe is helium. All of the other elements exist in much
lower abundances, much less than 1%. Carbon, nitrogen, oxygen, magnesium,
silicon, and iron are some of the common and more abundant heavier elements in
the Universe.
15. 11
SERIES OF FUSION REACTIONS
Step 1: 4 ( π») β π»π + 2π+
+ 2πππ’π‘πππππ + ππππππ¦
2
4
1
1
Step 2: 3 ( π»π) β πΆ + ππππππ¦
6
12
2
4
Step 3: πΆ + πΆ β ____(1)_____ + ππππππ¦
6
12
6
12
Step 4: πΆ + πΆ β ____(2)_____ + ππππππ¦
6
12
6
12
Step 5: πΆ + π»π β ____(3)_____ + ππππππ¦
2
4
6
12
Step 6: π + π β ____(4)_____ + ππππππ¦
8
16
8
16
Step 7: π + ____(5)_____ β ππ + ππππππ¦
10
20
8
16
Step 8: ____(6)____ + 7( π»π)
2
4
β ππ + ππππππ¦
28
56
Step 9: ππ
28
56
β ____(7)____ + π+ (πππ ππ‘ππ£π π½ πππππ¦)
Step 10: ____(8)____ β πΉπ + π+
(πππ ππ‘ππ£π π½ πππππ¦)
26
56
Step 11: πΉπ
26
56
+ π
0
1
β ___(9)___
Step 12: πΉπ
26
57
+ π
0
1
β ___(10)___
Step 13: πΉπ
26
58
+ π
0
1
β πΉπ
26
59
Highly massive stars convert its hydrogen to helium, helium to carbon,
carbon to magnesium, carbon and helium to oxygen, oxygen to sulfur, oxygen and
helium to neon, and silicon and helium to nickel. The unstable isotope of nickel
created undergoes positive beta decay and forms an isotope of cobalt that in turn
decays into iron. Positive beta decay is when a proton becomes a neutron, and a
positron is emitted.
A high-mass star creates many unstable isotopes of iron and actually goes
through a series of reactions that cause the star to make heavier and heavier nuclei
of elements, all the way up to Bismuth-209 - the heaviest known non-radioactive
nucleus.
16. 12
Let Us Remember
Let Us Assess
Read the questions carefully. Choose the best answer and write it on a
separate sheet of paper.
1. In the main sequence star, what element is formed when hydrogen fuse in
the starβs core?
A. Helium C. Carbon
B. Beryllium D. Oxygen
2. At approximately what temperature can nuclear reaction in a starβs core
occur?
A. 100,000 Kelvin C. 10,000,000 Kelvin
B. 1,000,000 Kelvin D. 100,000,000 Kelvin
3. Through what process are stars in the universe formed?
A. Nuclear fusion C. Nuclear decay
B. Nuclear fission D. Nuclear transmutation
4. How is the heavy element Carbon formed in a starβs core?
A. Explosion of the star C. Helium fusion
B. Hydrogen fusion D. Oxygen fusion
5. Where is the site of the formation of heavier elements in the universe?
A. Asteroid Belt C. Moon
B. Earth D. Star
Through this module, you have learned the following important concepts about star
formation and evolution.
β’ Stellar nucleosynthesis is the process by which heavier elements are formed
within stars.
β’ A main sequence star is formed from hydrogen fusion in a protostar.
β’ A red giant star is formed from the fusion of three helium atoms.
β’ A supergiant star is formed from the fusion of more alpha particles making
it more massive.
β’ A supernova is a star that explodes and releases a tremendous amount of
energy forming the elements heavier than iron.
β’ Evidences of star formation and evolution was traced in Infrared Radiation
(IR) and discovery of interstellar medium of gas and dust.
17. 13
6. How many Helium atom/s fuse/s together to produce Carbon?
A. 1 C. 3
B. 2 D. 4
7. What piece of evidence of star formation provides a view of stars due to their
heat energies?
A. Abundance of light elements C. Redshift
B. Infrared radiation D. Interstellar medium of gas &
dust
8. What heavier element can a supergiant star only produce up to?
A. Helium C. Iron
B. Carbon D. Magnesium
9. Which of the following is the correct sequence of the evolution of the star?
A. main sequence star, supergiant, red giant, supernova
B. main sequence star, red giant, supergiant, supernova
C. red giant, supergiant, main sequence star, supernova
D. supernova, main sequence star, red giant, supergiant
10. What stage of the evolution of the star produces the element Iron (Fe)?
A. Main sequence star C. Supergiant
B. Red giant D. Supernova
11. What fuel is needed in a red giant star to begin its fusion reaction?
A. Hydrogen C. Carbon
B. Helium D. Iron
12. What signals the doom or death of a star?
A. nucleosynthesis C. Supernova
B. Formation of iron D. Alpha fusion
13. How are elements heavier than Iron (Fe) formed?
A. Supernova C. Hydrogen Fusion
B. Helium Fusion D. Fusion of more alpha particles
14. What happens to the mass of a star as time goes on?
A. Lighter C. Constant
B. Heavier D. Equilibrium
15. What happens to the core temperature of a star as it ages/ evolves?
A. Decreases C. Constant
B. Increases D. Increases then decreases
18. 14
Let Us Enhance
Activity 3: Life and Death
After learning the lesson of this module, it is time to apply what you have
learned into real life situation. This will be done for you to find connection and
meaning of the lesson to your personal life.
Please read the text below and write your reflection in a separate sheet of
paper.
You can do it!
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
Your response in the reflective essay will be rated based on the rubric. Please
be guided accordingly.
The occurrence of supernova in the universe signals the
death of a star. In the same manner, life here on Earth has
its end. Do you believe in βlife after deathβ? Explain your
answer.
19. 15
Rubric in Assessing Reflective Essay
Criteria Poor
1 pt
Fair
2 pts
Good
3 pts
Excellent
4 pts
Depth of
Reflection
Response
shows lack of
reflection on
the selected
topic, with no
details.
Response
shows
shallow
reflection on
the selected
topic,
including a
few details
and
examples.
Response shows
a general
reflection on the
selected topic,
including some
supporting
details and
examples.
Response shows
an in-depth
reflection on the
selected topic,
including
supporting
details and
examples.
Quality of
Information
Information
is vague to
the main
topic.
Information
somehow
relates to the
main topic.
No details
and/or
examples are
provided.
Information
clearly relates to
the main topic. It
provides 1-2
supporting
details and/or
examples
Information
clearly relates to
the main topic.
It includes
several
supporting
details and/or
examples.
Structure &
Organization
Response is
unclear,
disorganized.
Response is
unclear, and
ideas are not
logically well
organized.
Response is
mostly clear, and
organized. Ideas
are conveyed in a
logical manner.
Response is
clear, and well
organized. Ideas
are conveyed in
a logical
manner.
Let Us Reflect
Stars are the most widely recognized astronomical objects, and represent
the most fundamental building blocks of galaxies. The age, distribution, and
composition of the stars in a galaxy trace the history, dynamics, and evolution of
that galaxy. Moreover, stars are responsible for the manufacture and distribution
of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics
are intimately tied to the characteristics of the planetary systems that may
coalesce about them. Consequently, the study of the birth, life, and death of stars
is central to the field of astronomy.
22. References
American Physical Society. 2012. google.com. September. Accessed June 6, 2020.
https://www.aps.org/publications/apsnews/201208/physicshistory.cfm .
Basic Education Assistance for Mindanao. 2008. "Atomic Structure and Nuclear
Radiation." BEAM Learning Guide.
β. 2018. "Energy and the Environment: Uses of Nuclear Radiation." BEAM
Learning Guide.
Borel, Brooke. 2013. google.com. May 13. Accessed June 2, 2020.
https://www.popsci.com/science/article/2013-04/making-new-elements/.
Commission on Higher Education. 2016. google.com. Accessed May 23, 2020.
https://drive.google.com/file/d/0B869YFOKEHr7SHFGVG5mVFFhcXc/view
Darling, David. n.d. google.com. Accessed June 23, 2020.
https://www.daviddarling.info/encyclopedia/T/technetium.html.
Ernest Lawrence Biographical. n.d. google.com. Accessed June 5, 2020.
https://www.nobelprize.org/prizes/physics/1939/lawrence/biographical/.
FamousScientist.org. n.d. google.com. Accessed June 6, 2020.
https://www.famousscientists.org/dmitri-mendeleev/.
2014. google.com. December 29. Accessed June 6, 2020.
https://www.famousscientists.org/henry-moseley/.
Krivit, Steven B. 2019. google.com. May 18. Accessed June 5, 2020.
https://news.newenergytimes.net/2019/05/18/rutherfords-reluctant-role-
in-nuclear-transmutation/.
Learner, Chemistry. n.d. google.com. Accessed June 23, 2020.
https://www.chemistrylearner.com/astatine.html.
Point, Assignment. n.d. google.com. Accessed June 23, 2020.
https://www.assignmentpoint.com/science/physics/neptunium.html.
n.d. Quipper School Link. Accessed May 25, 2020. https://link.quipper.com.
Religioso, Estrella E. Mendoza & Teresita F. 2000. Chemistry. Quezon City: Phoenix
Publishing House, Inc.
Ross, Rachel. 2018. google.com. December 5. Accessed June 6, 2020.
https://www.livescience.com/64241-x-ray-spectroscopy.html.
Christensen M (2019) How Do Stars Form?. Front. Young Minds. 7:92. doi:
10.3389/frym.2019.00092
BBC GCSE (2021) Accessed at
https://www.bbc.co.uk/bitesize/guides/zpxv97h/revision/1.
(Helmenstine, google.com, 2015)
23. For inquiries or feedback, please write or call:
Department of Education β Region XI Davao City Division
DepEd Davao City, Elpidio Quirino Ave., Davao City
Telefax: 224-3274
Email Address: davaocity.division@deped.gov.ph
