Integrated Science SME

Key Unit competence: To illustrate and describe the general
                                               structure of the solar system.

Introductory Activity 22

Observe the following illustration and answer the questions

Questions:
a) What do you see in the illustration above?
b) Can you suggest how the bodies identified in the illustration
above move? Explain to support your decision?
c) Explain how the earth receives light during the night?
d) What causes day and night? Explain your answer with possible
illustrations.
e) How do Kepler talk about the general structure of the solar
system? Justify your arguments with possible illustrations.

22.1. Astronomical scales

Activity 22.1

1. Student-teachers interpret reality from their perspective of the world
around them. As a result their everyday thinking about space and time
is often limited to local conditions; often at most perhaps hundreds of
kilometre or decades of years. Vast distances and times are central
ideas in ‘the changing Earth and its place in space’.

Questions: Read the paragraph above and try to answer the following
questions;

a) Explain how these ideas are very difficult for student-teachers to
grasp.

b) Explain why it has very important implications for their learning of
ideas about distances in space or very long spans of time.

22.1.1. Origin of the solar system

Our solar system originated from a giant cloud of gas and debris left from
the explosion of stars five billion years ago. Everything in the universe and
on Earth is made of this material. Scientific evidence implies that some rock
near the Earth’s surface is several billion years old.

The Earth’s surface is shaped by water (including ice) and wind over very
long times. The change is so slow that it is hard to observe rock erosion and
soil formation. Biological evolution is also difficult to observe due to the very
slow changes that occur.

22.1.2. Astronomical scale

Astronomy is the study of the universe, and when studying the universe,
we often deal with unbelievable sizes and unfathomable distances. To help
us get a better understanding of these sizes and distances, we can put them
to scale.

Scale is the ratio between the actual object and a model of that object.
Some common examples of scaled objects are maps, toy model kits, and
statues. Maps and toy model kits are usually much smaller than the object it
represents, whereas statues are normally larger than its analog.

Our solar system is immense in size. We think of the planets as revolving
around the sun but rarely consider how far each planet is from the sun or from
each other. Furthermore, we fail to appreciate the even greater distances to

the other stars. Astronomers refer to the distance from the sun to the Earth
as one“astronomical unit” or AU = approximately 150 million kilometres. This
unit provides an easy way to calculate the distances of the other planets
from the sun and build a scale model with the correct relative distances.

Viewed from Earth it is difficult to gauge the scale of the universe but
astrophysicists have developed techniques to help to do this. Stars and
galaxies are so far away than a new unit of distance measurement, the
light-year (ly),is often used. For light travelling at 3 x 108m/s, the distance
traveled in oneyear is:1 ly = (3 x 108 m/s) x (365 x 24 x 60 x 60 s) = 9.46 x
1015 m.

For specifying distances to the Sun and Moon, we usually use metres or
kilometres, but we could specify them in terms of light. The Earth-Moon
distance is 384 000 km, which is 1.28 light-seconds. The Earth-Sun distance
is 1.5 x 1011 m, or 150,000,000 km; this is equal to 8.3 light-minutes. Far out
in our solar system, the ninth planet, Pluto, is about 6 x 109km from the Sun,
or 6 x 10-4 ly. The nearest star tous, other than the sun, is Proxima Centauri,
about 4.3 ly away. (Note that the nearest star is about 10,000 times farther
from us than the outer reaches of our solar system.)

The Milky Way or our Galaxy is about 100 000 ly across; our sun is located
on one

of the spiral arms of the galaxy at a distance of 28,000 ly from the galactic
centre.

Application activity 22.1
1. Construct a time line to gain perspective of the vastness of time and
     our lifetime in reference to it. Examples of timelines are ‘the origins
     of the solar system’ and ‘life on Earth’. If a helpful scale is used a
     time line representing the age of the Earth can be displayed around
     the walls of their classroom.

2. Construct a scale model of the solar system with both distances
     and size of planets to scale. If an orange is used to represent the
     size of the sun then the model of the solar system should fit into the
     size of an average school oval.

22.2. Sun-earth-moon system: eclipses and phases of the
            moon

Activity 22.2

From our perspective, the three objects that have the greatest impact on
our lives are the Earth, Sun, and Moon. The Earth, of course, is the planet
beneath our feet. Without it, well, we wouldn’t have anything at all. The
Sun warms our planet, and with the Moon, creates the tides. Interpret the
figure below and try to answer the questions that follow:

Questions:
c) Describe how Earth’s movements affect seasons and cause day
     and night.

d) Explain solar and lunar eclipses.

e) Describe the phases of the Moon and explain why they occur.

f) Explain how movements of the Earth and Moon affect Earth’s
    tides

Eclipse, in astronomy is the obscuring of one celestial body by another,
particularly that of the sun or a planetary satellite. Two kinds of eclipses
involve the earth: those of the moon, or lunar eclipses; and those of the sun,
or solar eclipses. A lunar eclipse occurs when the earth is between the sun
and the moon and its shadow darkens the moon. A solar eclipse occurs
when the moon is between the sun and the earth and its shadow moves
across the face of the earth.

22.2.1.Lunar Eclipses
The earth, lit by the sun, casts a long, conical shadow in space. At any point
within that cone the light of the sun is wholly obscured.

A total lunar eclipse occurs when the moon passes completely into the
umbra. If it moves directly through the centre, it is obscured for about 2
hours. If it does not pass through the centre, the period of totality is less and
may last for only an instant if the moon travels through the very edge of the
umbra.

A partial lunar eclipse occurs when only a part of the moon enters the umbra
and is obscured. The extent of a partial eclipse can range from near totality,
when most of the moon is obscured, to a slight or minor eclipse, when
only a small portion of the earth’s shadow is seen on the passing moon.
Historically,the view of the earth’s circular shadow advancing across the
face of the moon was the first indication of the shape of the earth.

22.2.2.Solar eclipses
A solar eclipse occurs when the Moon passes in front of the Sun causing a
shadow to fall on certain portions of the Earth. The eclipse is not seen from
every place on Earth, but only from the locations where the shadow falls.

In areas outside the band swept by the moon’s umbra but within the
penumbra, the sun is only partly obscured, and a partial eclipse occurs.

Types of Solar Eclipses
Depending on what part of the shadow you are located in, there are three
types of eclipses:
• Total - A total eclipse is where the Sun is covered completely by the
Moon. The portion of the Earth that is in the umbra experiences a total
eclipse.
• Annular - An annular eclipse is when the Moon covers the Sun, but the
Sun can be seen around the edges of the Moon. An annular eclipse
occurs when the viewer is within the antumbra.
• Partial - A partial eclipse is when only a portion of the Sun is blocked
by the Moon. It occurs when the observer is within the penumbra.
Caution! Don’t Look at A Solar Eclipse. We should warn you here to never
look directly at a solar eclipse. Even though it appears darker, the harmful
rays of the Sun can still damage your eyes.

22.2.3. Phases of the moon
Like everything in the solar system except the Sun, the Moon does not
produce any light of its own. It only reflects sunlight. As the Moon moves
around Earth, different portions of the satellite are illuminated. This causes
the phases of the Moon, so that our view of the Moon goes from fully lit to
completely dark and back again.

There are different phases of the Moon that make it appear a little different
every day, but it looks the same again about every four weeks. The Moon
can sometimes be seen at night and sometimes during the day.

Phases of the Moon

• The Moon is full when Earth is between the Moon and the Sun and the
Moon’s nearside is entirely lit.

• The Moon is at first quarter phase about one week later, when the
Moon appears as a half-circle. Only half of the Moon’s lit surface is
visible from Earth.

• The Moon is in a new moon phase when the Moon moves between
Earth and the Sun and the side of the Moon facing Earth is completely
dark. Earth observers may be able to just barely see the outline of the
new moon because some sunlight reflects off the Earth and hits the
moon.

• Before and after the quarter-moon phases are the gibbous and crescent
phases. During the gibbous moon phase, the moon is more than half
lit but not full. During the crescent moon phase, the moon is less than
half lit and is seen as only a sliver or crescent shape.

One revolution of the Moon around Earth takes a little over 27 days 7 hours.
The Moon rotates on its axis in this same period of time, so the same face
of the Moon is always presented to Earth. Over a period, a little longer than
29 days 12 hours, the Moon goes through a series of phases, in which the
amount of the lighted half of the Moon we see from Earth changes. These
phases are caused by the changing angle of sunlight hitting the Moon. (The
period of phases is longer than the period of revolution of the Moon, because
the motion of Earth around the Sun changes the angle at which the Sun’s
light hits the Moon from night to night).

Application activity 22.2
1. What is a solar eclipse?
a) When the Moon passes in front of the Sun
b) When the Earth casts a shadow on the Moon
c) When the Sun is blocked by another planet
d) All of the above
e) None of the Above

2. What do we call the area of a solar eclipse where only a portion of
the Moon is in front of the Sun?
a) Umbra b) Antumbra c) Penumbra.

3) What do we call the area of a solar eclipse where the Moon covers
the Sun, but the outline of the Sun can still be seen?
a) Umbra b) Antumbra c) Penumbra

4) What do we call the area of a solar eclipse where the Moon completely
covers the Sun?
a) Umbra b) Antumbra c) Penumbra

5) What type of solar eclipse occurs when only a portion of the Sun is
blocked by the Moon?
a) Total   b) Lunar   c) Special   d) Annular    e) Partial.

6) What type of solar eclipse occurs when the Sun is completely covered
by the Moon?
a) Total    b) Lunar    c) Special    d) Annular    e) Partial.

7) What is a lunar eclipse?
a) When the Moon passes in front of the Sun.
b) When the Earth casts a shadow on the Moon.
c) When the Sun is blocked by another planet.
d) All of the above.
e) None of the Above.

8) What color will the moon sometimes appear during a lunar eclipse?
a) Green   b) Blue   c) Yellow    d) Red    e) purple.

9) Around how long can a solar eclipse last?
a) 1.5 minutes   b) 7.5 minutes   c) 30minutes    d) 1.5 hours e) 7.5
hours.

10) True or False: Looking directly at the Sun during a solar eclipse can
damage your eyes.

22.3. Solar system

Activity 22.3

Observe and interpret the image below and try to explain the structure of
the solar system based on the inner and outer planets.

Solar System is constituted by the Sun and everything that orbits the
Sun,including the planets and their satellites, the dwarf planets, asteroids,
and comets, and interplanetary dust and gas...

22.3.1. Inner planets and outer planets
In our Solar System, astronomers often divide the planets into two groups:
the inner planets and the outer planets. The inner planets are closer to
the Sun and are smaller and rockier. The outer planets are further away,
larger and made up mostly of gas.

The inner planets (in order of distance from the sun, closest to furthest)
are Mercury, Venus, Earth and Mars. After an asteroid belt come the outer
planets, Jupiter, Saturn, Uranus and Neptune. The interesting thing is, in
some other planetary systems discovered, the gas giants are actually quite
close to the sun. This makes predicting how our Solar System formed an
interesting exercise for astronomers. Conventional wisdom is that the young
Sun blew the gases into the outer fringes of the Solar System and that is why
there are such large gas giants there. However, some extra-solar systems
have “hot Jupiters” that orbit close to their Sun.

a. The Inner Planets
The four inner planets are called terrestrial planets because their surfaces
are solid (and, as the name implies, somewhat similar to Earth — although
the term can be misleading because each of the four has vastly different
environments). They’re made up mostly of heavy metals such as iron and
nickel, and have either no moons or few moons. Below are brief descriptions
of each of these planets based on this information from National Aeronautic
and Space Authority of the USA (NASA).

Mercury
Mercury is the smallest planet in our Solar System and also the closest. It
rotates slowly (59 Earth days) relative to the time it takes to rotate around
the sun (88 days). The planet has no moons, but has a tenuous atmosphere
(exosphere) containing oxygen, sodium, hydrogen, helium and potassium.
The NASA MESSENGER (Mercury Surface, Space Environment,
Geochemistry, and Ranging) spacecraft is currently orbiting the planet.

Venus

Venus was once considered a twin planet to Earth, until astronomers
discovered its surface is at a lead-melting temperature of 900 degrees
Fahrenheit (480 degrees Celsius). The planet is also a slow rotator, with
a 243-day long Venusian day and an orbit around the sun at 225 days. Its
atmosphere is thick and contains carbon dioxide and nitrogen. The planet
has no rings or moons and is currently being visited by the European Space
Agency’s Venus Express spacecraft.

Earth

Earth is the only planet with life as we know it, but astronomers have found
some nearly Earth-sized planets outside of our solar system in what could
be habitable regions of their respective stars. It contains an atmosphere
of nitrogen and oxygen, and has one moon and no rings. Many spacecraft
circle our planet to provide telecommunications, weather information and
other services.

Mars

Mars is a planet under intense study because it shows signs of liquid water
flowing on its surface in the ancient past. Today, however, its atmosphere
is a wispy mix of carbon dioxide, nitrogen and argon. It has two tiny moons
(Phobos and Deimos) and no rings. A Mars day is slightly longer than 24
Earthhours and it takes the planet about 687 Earth days to circle the Sun.
There’s a small fleet of orbiters and rovers at Mars right now, including the
large NASA Curiosity rover that landed in 2012.

b. The Outer Planets
Sometimes called Jovian planets or gas giants are huge planets swaddled
in gas. They all have rings and all of plenty of moons each.
Despite their size, only two of them are visible without telescopes: Jupiter
and Saturn. Uranus and Neptune were the first planets discovered since
antiquity, and showed astronomers the solar system was bigger than
previously thought. Below are brief descriptions of each of these planets
based on this information from NASA.

Uranus was first discovered by William Herschel in 1781. The planet’s day
takes about 17 Earth hours and one orbit around the Sun takes 84 Earth
years.

Its mass contains water, methane, ammonia, hydrogen and helium
surrounding a rocky core. It has dozens of moons and a faint ring system.
There are no spacecraft slated to visit Uranus right now; the last visitor was
Voyager 2 in 1986.

Jupiter

Jupiter is the largest planet in our Solar System and spins very rapidly
(10 Earth hours) relative to its orbit of the sun (12 Earth years). Its thick
atmosphere is mostly made up of hydrogen and helium, perhaps surrounding
a terrestrial core that is about Earth’s size. The planet has dozens of moons,
some faint rings and a Great Red Spot, a raging storm happening for the
past 400 years at least (since we were able to view it through telescopes).
NASA’s Juno spacecraft is en route and will visit there in 2016.

Saturn
Saturn is best known for its prominent ring system, seven known rings with
well-defined divisions and gaps between them.

How the rings got there is one subject under investigation. It also has dozens
of moons. Its atmosphere is mostly hydrogen and helium, and it also rotates
quickly (10.7 Earth hours) relative to its time to circle the Sun (29 Earth
years). Saturn is currently being visited by the Cassini spacecraft, which will
fly closer to the planet’s rings in the coming years.

Uranus

Neptune
Neptune is a distant planet that contains water, ammonia, methane,
hydrogen and helium and a possible Earth-sized core. It has more than a
dozen moons and six rings. The only spacecraft to ever visit it was NASA’s
Voyager 2 in 1989.

Comets
Comet, small icy body in space that sheds gas and dust. Like rocky asteroids,
icy comets are ancient objects left over from the formation of the solar system
about 4.6 billion years ago. Some comets can be seen from Earth with the
unaided eye.

Comets typically have highly elliptical (oval-shaped), off-centre orbits that
swing near the Sun. When a comet is heated by the Sun, some of the ice on
the comet’s surface turns into gas directly without melting. The gas and dust
freed from the ice can create a cloud (coma) around the body (nucleus) of
the comet.

More gas and dust erupt from cracks in the comet’s dark crust. High-energy
charged particles emitted by the Sun, called the solar wind, can carry the gas
and dust away from the comet as a long tail that streams into space. Gas in
the tail becomes ionized and glows as bluish plasma, while dust in the tail is
lit by sunlight and looks yellowish. This distinctive visible tail is the origin of
the word comet, which comes from Greek words meaning “long-haired star.”

Humans have observed comets since prehistoric times. Comets were long
regarded as supernatural warnings of calamity or signs of important events.

Astronomers and planetary scientists now study comets for clues to the
chemical makeup and early history of the solar system, since comets have
been in the deep-freeze of outer space for billions of years. Materials in
comets may have played a major role in the formation of Earth and the origin
of life. Catastrophic impacts by comets may also have affected the history of
life on Earth, and they still pose a threat to humans.

A meteorite is a rock from outer space; it’s a piece of rock that has
reached Earth from outer space. It can also be defined as a fiery mass of
rock fromspace, a mass of rock from space that burns up after entering the
Earth’s atmosphere.

Meteorite, meteor that reaches the surface of Earth or of another planet
before it is entirely consumed. Meteorites found on Earth are classified into
types, depending on their composition: irons, those composed chiefly of
iron, a small percentage of nickel, and traces of other metals such as cobalt;
stones, stony meteors consisting of silicates; and stony irons, containing
varying proportions of both iron and stone.

Although most meteorites are now believed to be fragments of asteroids or
comets, recent geochemical studies have shown that a few Antarctic stones
came from the Moon and Mars, from which they presumably were ejected
by the explosive impact of asteroids. Asteroids themselves are fragments of
planetesimals, formed some 4.6 billion years ago, while Earth was forming.
Irons are thought to represent the cores of planetesimals, and stones (other
than the aforementioned Antarctic ones) the crust. Meteorites generally have
a pitted surface and fused, charred crust. A meteorite that landed in Texas
in 1998 was found to have water trapped in its rock crystals. The discovery
helped scientists theorize about whether water exists in other parts of the
solar system.

The largest known meteorite, estimated to weigh about 60 metric tons, is
situated at Hoba West near Grootfontein, Namibia. The next largest, weighing
more than 31 metric tons, is the Ahnighito (the Tent); it was discovered,
along with two smaller meteorites, in 1894 near Perlernerit (Cape York),
Greenland, by American explorer Robert Edwin Peary.

Composed chiefly of iron, the three masses had long been used by the Inuit
as a source of metal for the manufacture of knives and other weapons.

Asteroids

Asteroid, small rocky or metallic body that orbits the Sun. Hundreds of
thousands of asteroids exist in the solar system. Asteroids range in size
from a few metres to over 500km wide. They are generally irregular in shape
and often have surfaces covered with craters. Like icy comets, asteroids are
primitive objects left over from the time when the planets formed, making
them of special interest to astronomers and planetary scientists.

On the figure 12.10, Asteroid Mathilde, left, is the third and the largest
asteroid ever to be viewed at close range. The Near Earth Asteroid
Rendezvous(NEAR) spacecraft flew by Mathilde in late June 1997. Asteroids
Gaspra and Ida, centre and right, photographed by the Galileo orbiter in 1991
and 1993, respectively, are smaller and more oblong-shaped than Mathilde.
The three asteroids are partially obscured by shadows.

Most asteroids are found between the orbits of the planets Mars and Jupiter
in a wide region called the asteroid belt. Scientists think Jupiter’s gravity
prevented rocky objects in this part of the solar system from forming into
a large planet. The giant planet Jupiter’s gravity also helped throw objects
out of the asteroid belt. The hundreds of thousands of asteroids now in the
asteroid belt represent only a small fraction of the original population.

Thousands of asteroids have orbits that lie outside the asteroid belt. Some
of these asteroids have paths that cross the orbit of Earth. Many scientists
think that an asteroid that hit Earth 65 million years ago caused the extinction
of the dinosaurs. Because asteroids can pose a danger to people and other
life on Earth, astronomers track asteroids that come near our planet. Space
scientists are also studying ways to deflect or destroy an asteroid that might
strike Earth in the future.

Many scientists believe that a large asteroid or comet struck Earth about
65 million years ago, changing the Earth’s climate enough to kill off the
dinosaurs.

Application activity 22.3
1. Which of the following is true about asteroids?
a) They are made of rock and metal b) The orbit the Sun c) They
are in outer space d) All of the above e) None of the Above.

2. According to the article, what are most asteroids shaped like?
a) Ball b) Box c) Potato d) Triangle. e) Orange.

3. What two metals are metallic asteroids mostly made of?
a) Iron and nickel b) Silver and gold c) Magnesium and copper d)
Aluminum and zinc e) Lead and iron

4.What is the most common type of asteroid?
a) Metallic b) Carbon c) Rocky d) Gas e) Round

5. The asteroid belt is located in orbit between what two planets?
a) Earth and Mars b) Jupiter and Saturn c) Venus and Mercury
d) Neptune and Saturn e) Mars and Jupiter.

6.What is the largest asteroid in the Solar System?
a) Vesta b) Ceres c) pallas d) hygiea

7.What is the largest of the carbon asteroids?
a) Vesta b) Ceres c) pallas d) hygiea

8.What is the brightest asteroid when viewed from Earth?
a) Vesta b) Ceres c) pallas d) hygiea

9. What asteroid is the largest body in the Solar System that is not
round?
b) Vesta b) Ceres c) pallas d) hygiea

10. True or False: Most asteroids that hit the Earth are small enough to
explode when they hit the Earth's atmosphere.

22.4. Kepler’s Laws

Activity 22.4

1. It has been mentioned that planets move not on circle but follow an
elliptical curve. State laws that govern this type of motion.
2. How do you relate the period and the mean radius of planet’s orbit?

Johannes Kepler proposed three laws of planetary motion. Kepler was able
to summarize the carefully collected data of his mentor with three state-
ments that described the motion of planets in a sun-centered solar system.
Kepler’s efforts to explain the underlying reasons for such motions are no
longer accepted; nonetheless, the actual laws themselves are still considered
an accurate description of the motion of any planet and any satellite.
Kepler’s three laws of planetary motion can be described as follows:

22.4.1. First Kepler’s law

Statement
“The path of the planets about the sun is elliptical in shape, with the center
of the sun being located at one focus.” (The Law of Ellipses)

Figure 22.10 (a) An ellipse is a curve in which the sum of the distances from
a point on the curve to two foci (f1 and f2) is a constant. From this definition,
you can see that an ellipse can be created in the following way. Place a pin
at each focus, and then place a loop of string around a pencil and the pins.
Keeping the string taught, move the pencil around in a complete circuit. If
the two foci occupy the same place, the result is a circle—a special case of
an ellipse.

Figure 22.10. (b) For an elliptical orbit, if m << M , then m follows an elliptical
path with M at one focus. More exactly, both m and M move in their own
ellipse about the common center of mass.

22.4.2. Kepler’s Second Law

Kepler’s second law states that“A line segment joining a planet and the Sun
sweeps out equal areas during equal intervals of time.”

Therefore, an imaginary line drawn from the center of the sun to the center
of the planet will sweep out equal areas in equal intervals of time. (The Law
of Equal Areas).

Consider Figure 22.14 The time it takes a planet to move from position A to
B, sweeping out area A1, is exactly the time taken to move from position C
to D, sweeping area A2, and to move from E to F, sweeping out area A3.
These areas are the same: A1 = A2 = A3.

Comparing the areas in the figure and the distance traveled along the ellipse
in each case, we can see that in order for the areas to be equal, the planet
must speed up as it gets closer to the Sun and slow down as it moves away.
But we will show that Kepler’s second law is actually a consequence of the
conservation of angular momentum, which holds for any system with only
radial forces.

22.4.3. Kepler’s Third Law (The Law of Harmonies)

Statement

“The Square of the orbital period of a planet is proportional to the cube of
the semi-major axis of its orbit”.
In Satellite Orbits and Energy, we derived Kepler’s third law for the special
case of a circular orbit.

Application activity 22.4
1. Write in symbol the law of harmonies

2. Kepler’s second law is the consequence of which physical quantity.
Write the symbolical definition of that physical quantity.

3. Explain the law of equal area.

22.5. Star Patterns: Constellations

Activity 22.5

1. Research on star patterns and do report about constellations.
2. Research on uses of constellation.

Constellations
A constellation is a group of visible stars that form a pattern when viewed
from Earth. The pattern they form may take the shape of an animal,
a mythological creature, a man, a woman, or an inanimate object such as a
microscope, a compass, or a crown.

How many constellations are there? The sky was divided up into 88
different constellations in 1922. This included 48 ancient constellations
listed by the Greek astronomer Ptolemy as well as 40 new constellations.

Star Maps
The 88 different constellations divide up the entire night sky as seen from
all around the Earth. Star maps are made of the brightest stars and the
patterns that they make which give rise to the names of the constellations.
The maps of the stars represent the position of the stars as we see them
from Earth. The stars in each constellation may not be close to each other
at all. Some of them are bright because they are close to Earth while
others are bright because they are very large stars.

Hemispheres and Seasons

Not all of the constellations are visible from any one point on Earth. The
star maps are typically divided into maps for the northern hemisphere and
maps for the southern hemisphere. The season of the year can also affect
what constellations are visible from where you are located on Earth

Famous constellations
Here are a few of the more famous constellations:

Orion
Orion is one of the most visible constellations. Because of its location,
it can be seen throughout the world. Orion is named after a hunter
from Greek mythology. Its brightest stars are Betelgeuse and Rigel.

Ursa Major
Ursa Major is visible in the northern hemisphere. It means “Larger Bear”
in Latin. The Big Dipper is part of the Ursa Major constellation. The Big
Dipper is often used as a way to find the direction north.

Ursa Minor
Ursa Minor means “Smaller Bear” in Latin. It is located near Ursa Major and
also has the pattern of a small ladle called the Little Dipper as part of its
larger pattern.

Draco constellation
The Draco constellation can be viewed in the northern hemisphere. It means
“dragon” in Latin and was one of the 48 ancient constellations.

Pegasus
The Pegasus constellation is named after the flying horse by the same name
from Greek mythology. It can be seen in northern sky.

The zodiac

The Zodiac constellations are the constellations that are located within
a band that is about 200 wide in the sky. This band is considered special
because it s the band where the sun, the moon and the planets all move.
There are 13 Zodiac constellations. Twelve of these are also used as signs for
the zodiac calendar and astrology. These are Capricornus, Aquarius, pisces

Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius and
Ophiuchus.

Uses for Constellations

Constellations are useful because they can help people to recognize stars in
the sky. By looking for patterns, the stars and locations can be much easier
to spot. The constellations had uses in ancient times. They were used to
help keep track of the calendar. This was very important so that people knew
when to plant and harvest crops. Another important use for constellations
was navigation. By finding Ursa Minor it is fairly easy to spot the North
Star (Polaris). Using the height of the North Star in the sky, navigators
could figure out their latitude helping ships to travel across the oceans.

Application activity 22.5

1. What is a constellation?
a) A group of stars from the same galaxy.
b) A group of stars that are physically close to each other.
c) A group of visible stars that make a pattern when viewed from
Earth.
d) All of the above.
e) None of the Above.

2.How many constellations are there?
a) 12 b) 22 c) 44 d) 88 e) 120

3. What constellation was named after a flying horse?
a) Orion b) Ursa Minor c) Ursa Major d) Draco e) Pegasus

4. What constellation has the Little Dipper as part of its pattern?
a) Orion b) Ursa Minor c) Ursa Major d) Draco e) Pegasus

5. What constellation was named after a hunter from Greek mythology?
a) Orion b) Ursa Minor c) Ursa Major d) Draco e) Pegasus

6. What constellation has the Big Dipper as part of its pattern?
a) Orion b) Ursa Minor c) Ursa Major d) Draco e) Pegasus

7. True or False: All the constellations are visible from anywhere on
Earth throughout the year.

8. What group of constellations are used in astrology?
a) Ursa constellations b) Predictive constellations c) Northern
constellations d) Zodiac constellations e) Ancient constellations.

9. How are constellations useful?
a) To help locate stars b) To keep track of the calendar c) To
navigate d) To know when to plant crops. e) All of the above

Skills lab 22

1. With help of internet, visit youtube.com and watch “Seasons- what
causes seasons”. watch again the video , summarize the causes and
share the findings with your classmate and schoolmates.

2. Using local materials make a demonstration explaining Moon phases.

End unit assessment 22

1. Why does the moon seem to change its shape every night? Why
can I see the moon in the daytime?

2. What are the Moon phases in order?

3. What is an approximation of largest meteorite?

4. What is the role of Constellations?

5. Which physical quantity is conserved in the case of law of areas?

6. With the help of diagrams explain types of eclipses.