Physical Science
Quarter 2 – Module 3
Modern Astronomy
Physical Science
Alternative Delivery Mode
Quarter 2 – Module 3: Modern Astronomy
First Edition 2020
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Published by the Department of Education
Secretary: Leonor Magtolis Briones
Undersecretary: Diosdado M. San Antonio
Development Team of the Module
Writers: Jerwin A. Gutierrez and X-handi B. Fallarna
Editors: Priscilla D. Domino, Felipa A. Morada
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Physical Sciences
Quarter 2 – Module 3
Modern Astronomy
Introductory Message
For the facilitator:
Welcome to the Physical Science Grade 11 Alternative Delivery Mode (ADM)
Modules on Modern Astronomy!
This module was collaboratively designed, developed and reviewed by educators
both from public and private institutions to assist you, the teacher or facilitator in
helping the learners meet the standards set by the K to 12 Curriculum while
overcoming their personal, social, and economic constraints in schooling.
This learning resource hopes to engage the learners into guided and independent
learning activities at their own pace and time. Furthermore, this also aims to help
learners acquire the needed 21st century skills while taking into consideration
their needs and circumstances.
In addition to the material in the main text, you will also see this box in the body of
the module:
Notes to the Teacher
This contains helpful tips or strategies
that will help you in guiding the learners.
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. Furthermore, you are expected to encourage and assist
the learners as they do the tasks included in the module.
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For the learner:
Welcome to the Physical Science 11 Alternative Delivery Mode (ADM) Module on
Modern Astronomy!
The hand is one of the most symbolized part of the human body. It is often used to
depict skill, action and purpose. Through our hands we may learn, create and
accomplish. Hence, the hand in this learning resource signifies that you as a
learner is capable and empowered to successfully achieve the relevant
competencies and skills at your own pace and time. Your academic success lies in
your own hands!
This module was designed to provide you with fun and meaningful opportunities
for guided and independent learning at your own pace and time. You will be
enabled to process the contents of the learning resource while being an active
learner.
This module has the following parts and corresponding icons:
What I Need to Know
This will give you an idea of the skills or
competencies you are expected to learn in
the module.
What I Know
This part includes an activity that aims to
check what you already know about the
lesson to take. If you get all the answers
correct (100%), you may decide to skip this
module.
What’s In
This is a brief drill or review to help you link
the current lesson with the previous one.
What’s New
In this portion, the new lesson will be
introduced to you in various ways such as a
story, a song, a poem, a problem opener, an
activity or a situation.
What is It
This section provides a brief discussion of
the lesson. This aims to help you discover
and understand new concepts and skills.
What’s More
This comprises activities for independent
practice to solidify your understanding and
skills of the topic. You may check the
answers to the exercises using the Answer
Key at the end of the module.
What I Have
Learned
This
includes
questions
or
blank
sentence/paragraph to be filled into process
what you learned from the lesson.
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What I Can Do
This section provides an activity which will
help you transfer your new knowledge or
skill into real life situations or concerns.
Assessment
This is a task which aims to evaluate your
level of mastery in achieving the learning
competency.
Additional
Activities
In this portion, another activity will be given
to you to enrich your knowledge or skill of
the lesson learned. This also tends retention
of learned concepts.
Answer Key
This contains answers to all activities in the
module.
At the end of this module you will also find:
References
This is a list of all
developing this module.
sources used in
The following are some reminders in using this module:
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. Don’t forget to answer What I Know before moving on to the other activities
included in the module.
3. Read the instruction 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 through with it.
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!
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What I Need to Know
This module was designed and written with you in mind. It is here to help you to
explain how Tycho Brahe’s innovations and extensive collection of data in
observational astronomy paved the way for Johannes Kepler’s discovery of his laws
of planetary motion. The scope of this module permits it to be used in many
different learning situations. The language used recognizes the diverse vocabulary
level of students. The lessons are arranged to follow the standard sequence of the
course. But the order in which you read them can be changed to correspond with
the textbook you are now using.
The module contains discussion about the five noted scientists who made
important discoveries that gave rise to the birth of modern astronomy.
After going through this module, you are expected to:
1. discuss the notable contributions of some of the notable astronomers of
modern astronomy;
2. describe the relationship of Brahe and Kepler to the discovery of planetary
motion; and
3. realize the importance of the laws of planetary motion.
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What I Know
Word Play!
Directions: Use the pool of words in the box to complete the puzzle.
Across
1. Earth does this around the sun once a year.
1. Dark region of the Sun due to lower temperature.
8. an obscuring of the light from one celestial body by the passage of
another between it and the observer or between it and its source of
illumination
12. are three scientific laws describing the motion of planets around the
Sun, by Johannes Kepler
15. the perimeter of a circle or ellipse
2
Down
1. It is the shape of the Earth and some other planets. It is like a sphere
squashed from the top so the diameter from pole to pole is less than the
diameter from equator to equator.
3. An imaginary line through Earth.
Down
4. A representation of the sun-Earth-moon system.
6. Discovered by Galileo to look at the moon, discover the four satellites of
Jupiter, observe supernova, and discover sunspot.
7. Developed and formalized Galileo's concept of inertia.
9. A displacement or difference in the apparent position of an object viewed
along two different lines of sight, and is measured by the angle or semiangle of inclination between those two lines.
10. Justified his Earth-centered model and explained retrograde motion
through cycles and epicycles.
11. Earth's path in space.
13. His accurate measurements of Mars were his greatest contributions
to astronomy.
14. Developed a heliocentric system wherein the orbits were elliptical
rather than circular. This advanced the Sun-centered view.
Pool of Words
parallax
circumference
Planetary motion
oblate spheroid
eclipse
model
telescope
Ptolemy
axis
revolve
orbit
Newton
Kepler
sunspots
Tycho Brahe
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Lesson
3
Modern Astronomy
Throughout human history, scientists have struggled to understand
what they see in the night sky. Famous astronomers — many of them great
scientists who mastered many fields — explained the heavens with varying
degrees of accuracy. Over the centuries, a geocentric view of the universe —
with Earth at the center of everything — gave way to the proper
understanding we have today of an expanding universe in which our galaxy
is but one of billions. On this list are some of the most famous scientists
from the early days of astronomy through the modern era, and a summary
of some of their achievements.
After 14 centuries since Ptolemy, five noted scientists made important
discoveries that gave rise to the birth of modern astronomy. These were
Nicolaus Copernicus, Tycho Brahe, Johannes Kepler, Galileo Galilei and
Isaac Newton.
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What’s In
Matching Type. Directions: Match the five noted scientists in column A with their
important discoveries in column B. Write the letter on the space provided before
each number.
Column A
________1. Nicolaus Copernicus
________2. Tycho Brahe
________3. Johannes Kepler
________4. Galileo Galilei
________5. Isaac Newton
Column B
A. He developed and formalized Galileo’s
concept of inertia. He conceptualized the
force of gravity and he was able to provide
an explanation for the elliptical orbits.
B. He was the greatest Italian scientist of the
Renaissance. Due to the telescope, he
was able to discover and observe
important astronomical facts.
C. Using his mentor’s data, he formulated
the three laws of planetary motion: the law
of Ellipse, Law of Equal Areas, and the
Law of harmonies.
D. He believed that only the sun and the
moon revolved around the earth; the
other planets revolved around the sun,
which itself revolved around the earth.
E. He was a student of Plato. For him, the
earth is spherical in shape since it
always casts a curved shadow when it
eclipses the moon.
F. He considered the sun as the stationary
center of the universe. He classified
earth as a planet just like Mercury,
Venus, Mars, Jupiter, and Saturn.
Notes to the Teacher
Is science worth dying for? This may sound absurd and unlikely but for
some scientist risking their lives for the truth is one of their greatest
achievements.
Students will analyze and discuss the implications of scientists defying
cultural beliefs in older times and what science would be like today
without the scientific analysis and discoveries of Tycho Brahe and
Johannes Kepler.
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What’s New
Some Astronomical Terms for
Students astronomical unit (AU)
the unit of length defined as the average distance between Earth and the
Sun; this distance is about 1.5 × 108 kilometers or 1.5 x 1011 metres
eccentricity
in an ellipse, the ratio of the distance between the foci to the major axis
ellipse
a closed curve for which the sum of the distances from any point on the
ellipse to two points inside (called the foci) is always the same
focus
(plural: foci) one of two fixed points inside an ellipse from which the sum of
the distances to any point on the ellipse is constant
Kepler’s first law
each planet moves around the Sun in an orbit that is an ellipse, with the
Sun at one focus of the ellipse
Kepler’s second law
the straight line joining a planet and the Sun sweeps out equal areas in
space in equal intervals of time
Kepler’s third law
the square of a planet’s orbital period is directly proportional to the cube of
the semimajor axis of its orbit
major axis
the maximum diameter of an ellipse
orbit
the path of an object that is in revolution about another object or
point orbital period (P)
the time it takes an object to travel once around the
Sun orbital speed
the speed at which an object (usually a planet) orbits around the mass of
another object; in the case of a planet, the speed at which each planet moves
along its ellipse
semimajor axis
half of the major axis of a conic section, such as an ellipse
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What is It
Tycho Brahe
Tycho Brahe was a Danish astronomer and nobleman who made accurate
observations of the movement of celestial bodies in an observatory built for
him by King Frederick II of Denmark in 1576. He was able to invent different
astronomical instruments, with the help of his assistants, and made an
extensive study of the solar system. He was able to determine the position of
777 fixed stars accurately.
Johannes Kepler
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When King Frederick II died, and the successor did not fully support Brahe’s
work, he moved to Prague in 1599 where he was supported by Emperor
Rudolf II and worked as an imperial mathematician. Emperor Rudolf II
recommended Johannes Kepler to work for him as an assistant. Kepler was
born to a poor German family and studied as a scholar at the University of
Tübingen in 1589.
Brahe and Kepler's Work
Brahe and Kepler had an unsteady working relationship. Kepler was Brahe's
assistant. However, Brahe mistrusted Kepler with his astronomical data in
fear of being shadowed by his assistant.
Brahe assigned to Kepler the interpretation of his observations of Mars,
whose movement did not match Brahe’s calculations. Kepler was tasked to
figure out what path Mars followed as it revolved around the Sun. It was
believed by many scientists that Brahe gave this task to Kepler to keep him
occupied and left Brahe to develop his laws of planetary motion.
Kepler's Discoveries from Brahe's Data
Kepler postulated that there must be a force from the Sun that moves the planets.
He was able to conclude that this force would explain the orbit of Mars and the
Earth, including all the other planets, moved fastest when it is nearest from the
Sun and moved slowest when it is farthest from the Sun.
Eventually, Brahe decided to give all his data to Kepler hoping that he would be
able to prove his Tychonic system and put together new tables of astronomical
data. This table was known as Rudolphine Tables, named after the Roman emperor
and was useful in determining the positions of the planets for the past 1000 years
and the future 1000 years. This table was the most accurate table that is known to
the astronomical world.
After Brahe died in 1601, Emperor Rudolf II assigned Kepler as the new imperial
mathematician, and all of Brahe’s writings, instruments, and the Rudolphine
tables were passed on to him. From Brahe’s data, Kepler was able to formulate his
laws of planetary motion: the law of ellipses, the law of equal areas, and the law of
harmonies.
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Kepler’s Laws of Planetary Motion
First Law - The Law of Ellipses
When Kepler tried to figure out Mars’ orbit, it did not fit the then-famous theory
that a planet follows a circular path. He then postulated that instead of a circular
path, planets follow an oval or an ellipse orbit.
This orbit matched his calculations and explained the “irregularities” in the
movement of Mars. He was able to formulate his first law of planetary motion, the
law of ellipses which describes that the actual path followed by the planets was
elliptical, not circular, with the Sun at one focus of the ellipse.
Second Law - The Law of Equal Areas
The second law, which is the law of equal areas states that when an imaginary line
is drawn from the center of the Sun to the center of a planet, the line will sweep out
an equal area of space in equal time intervals.
Planet
P
A
B
A
B
Elliptical orbit
Figure 4: The figure shows the Kepler’s 2nd Law or The
Law of Equal Areas
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The law describes how fast a planet moves in its orbit. A planet moves fastest when
it is nearest the Sun and slowest when it is farthest from the Sun, and still, the
same area is swept out by the line in equal amounts of time.
Third Law - The Law of Harmonies
The law of harmonies, which is the third law, describes that the square of a
planet’s orbital period (T2) is proportional to the cube of a planet’s average distance
from the Sun (R3). It states that that the ratio of the squares of the periods of two
planets is equal to the ratio of the cubes of the average distances of these two
planets from the Sun or:
where the subscript 1 indicates planet 1 and subscript 2 indicates
planet 2.
50000
Neptune
10000
Uranus
1000
Saturn
100
Jupiter
10
Mars
1
Earth
Venus
Mercury
10
100
1000
10000
Square of Orbital Period (Yr2)
Figure 4: The figure shows the Kepler’s 3rd Law or The Law
of Harmonies
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What’s More
Our understanding of the elliptical motion of planets about the Sun spanned
several years and included contributions from many scientists. Answer the
questions below. Write your answers on a separate sheet of paper.
Q1. Which scientist is credited with the collection of the data necessary to support
the planet's elliptical motion?
A1. _____________________________________
Q2. Which scientist is credited with the long and difficult task of analyzing the
data?
A2. _____________________________________
3. Which scientist is credited with the accurate explanation of the
data? A3. _____________________________________
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What I Have Learned
Fill in the blanks with the correct answer. Write your answers on a separate sheet
of paper.
1. ___________________ was a Danish astronomer and nobleman who made accurate
observations of the movement of celestial bodies.
2. ___________________ was a German astronomer and mathematician who worked
as an assistant to Brahe and formulated the three laws of planetary motion based
on Brahe’s extensive astronomical data.
3. ____________________ states that planets follow an elliptical orbit.
4_____________________ states that when an imaginary line is drawn from the center
of a planet to the center of the Sun, an equal amount of space is swept in equal
amount of time.
5. __________________ states that the ratio of the squares of the period of two
planets is equal to the ratio of the cubes of the planets’ average distance from the
Sun.