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Grade 9 Science
Unit 1/Chapter 10
What we know about the universe has taken us thousands of years to learn.
Our scientific knowledge had been based on the work astronomers who
experimented, collected evidence and found relationships.
Stars – give off light and heat and are very far away. Ex. the Sun
The sun is a star!
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Celestial Body – is a natural object out in space. Examples - planet, moon, asteroid,
comet, or a star.
Planets
moon
asteroid
comet
star
(Many years ago farmers made note of the movement of these bodies and used
them as their calendar. When certain stars were visible at certain times of the
night, they knew it was time to plant their crops)
Motion of Celestial Bodies
1)Moon – a celestial body that orbits a planet. The earth’s Moon orbits the earth
every 28 days. The Moon is our only natural satellite. The nearside hemisphere is
the side of the Moon that always faces Earth. Therefore, it does not rotate.
Other planets also have Moons. The amount of the Moon’s surface that is lit by the
sun changes throughout the month.
2)Sun – follows the same ecliptic path through the sky every day. Nine plants along
with asteroids and comets orbit the Sun. Some of those lie beyond Pluto but all are
controlled by the Sun’s powerful gravity.
Grade 9 Science
Unit 1/Chapter 10
3)Asteriods – one of the many rocky or metal bodies in the solar system, most of
which orbit the Sun between Mars and Jupiter. Not all asteroids orbit in this main
belt. Other asteroids have wide elliptical orbits that cross the orbit of Earth.
4)Comet – a small body made up of rocky material and ice that occur in the Kuper
Belt and Oort Cloud; when a comet is bumped into the inner solar system, the Sun’s
light may make the comet’s tail visible from earth. Comets orbit in a different
direction than planets. Comet’s orbits can be above or below the orbit of Earth.
Comet Halley is probable the most famous, it appears every 75 or 76 years and last
flew past Earth in 1986.
Grade 9 Science
Unit 1/Chapter 10
5)Planet – a celestial body that orbits one or more stars. It is large enough that its
own gravity holds it in a spherical shape and is the only body occupying it’s orbital
path. Planets in our galaxy were named after Roman Gods (Mercury, Venus, mars,
Jupiter and Saturn). As the planets revolve around the Sun they orbit at different
rates along their ecliptic path. The planets inside the Earth’s orbit (Mercury and
Venus) seem to race through the sky compared to the other planets. Most planets
have at least one moon orbiting them. The four largest planets also have rings.
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Galaxy – an enormous collection of gases, dust, and billions of stars held together
by gravity. There are millions of other stars in the universe.
-We live in the Milky Way Galaxy
-These are the stars you see at night
-This is the Andromeda Galaxy
Grade 9 Science
Unit 1/Chapter 10
Universe -is commonly defined as the totality of everything that exists, including
all space, time, matter, energy, planets, stars, galaxies, intergalactic space, and
beyond. The Universe had a beginning and it continues to expand.
Constellations – a distinctive pattern in the night sky formed by a group of starts.
The pattern often looks like a familiar object such as an animal.
- 88 constellations have been named. Because we live in the northern hemisphere
we cannot see 20 constellations that can be seen in the southern hemisphere.
Examples – Ursa Major, Ursa Minor, Orion, Cassopiopea, and Leo (see page 354).
There are 12 Zodiac Constellations. Which one is yours?
Orion’s Belt - Alnitak, Alnilam and Mintaka. These three prominent stars in the
central regions of the constellation of Orion align to form the 'belt' of the Hunter.
Alphabetical listing of constellations
Grade 9 Science
Unit 1/Chapter 10
(Study all of these for a chapter test...Just kidding  Do you recognize many of them?)
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Andromeda
Aquila
Boötes
Canes Venatici
Carina
Cetus
Coma Berenices
Crater
Dorado
Fornax
Horologium
Lacerta
Libra
Mensa
Norma
Pavo
Pictor
Pyxis
Scorpius
Sextans
Triangulum Australe
Vela
Antlia
Ara
Caelum
Canis Major
Cassiopeia
Chamaeleon
Corona Austrina
Crux
Draco
Gemini
Hydra
Leo
Lupus
Microscopium
Octans
Pegasus
Pisces
Reticulum
Sculptor
Taurus
Tucana
Virgo
Apus
Aries
Camelopardalis
Canis Minor
Centaurus
Circinus
Corona Borealis
Cygnus
Equuleus
Grus
Hydrus
Leo Minor
Lynx
Monoceros
Ophiuchus
Perseus
Piscis Austrinus
Sagitta
Scutum
Telescopium
Ursa Major
Volans
Aquarius
Auriga
Cancer
Capricornus
Cepheus
Columba
Corvus
Delphinus
Eridanus
Hercules
Indus
Lepus
Lyra
Musca
Orion
Phoenix
Puppis
Sagittarius
Serpens
Triangulum
Ursa Minor
Vulpecula
Asterism – is a smaller group of stars forming patterns within a constellation. It is
not a constellation. The Big Dipper is one of the most famous and visible patterns
Grade 9 Science
Unit 1/Chapter 10
in the northern sky. The Big Dipper is not a constellation but a smaller group of
stars that are part of the constellation Ursa Major (Great Bear).
Here are some more asterisms.
Circumpolar Constellations – a constellation that never appears to “set” or dip
below the horizon. They are always above the horizon, even in the daytime.
Whether a constellation is Circumpolar for you depends on where you
geographically live. For example, if you live in the northern hemisphere Ursa Major,
Ursa Minor and Cassiopeia would be circumpolar constellations. If you lived in
Australia they would not be.
The circumpolar stars are called that because they circle the pole, or the pole
star. The point in the sky around which the dome of the sky appears to rotate is
the Pole Star or Polaris in the Northern Hemisphere.
Grade 9 Science
Unit 1/Chapter 10
These are our circumpolar Constellations.
Seasonal Constellations – because the Earth moves around the Sun every year, we
see a different part of the sky every season. (See page 361).
Fall – Pegasus
Winter – Orion the Hunter
Spring – Leo
Summer - Cygnus
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Grade 9 Science
Unit 1/Chapter 10
Models of the Early Universe
As technology has improved so has our understanding the universe.
Early Astronomers – built observatories to track the movement in the skies. In the
17th century the first telescope was invented and allowed people to see detail such
as the craters in the Moon.
Ancient Observations – early people were very aware of daily and seasonal changes
in their everyday lives. Fisherman used the stars to navigate by. Hunters watched
the changing phases of the Moon (in a month) and the changing path of the Sun (in
a year). Early people used this information to get ready for the seasons, animal
migration, flooding rivers, and other natural phenomena.
Several sophisticated structures were built around the world to observe and track
celestial movement (page 367); Cichen Itza in Mexico, Stongehenge in England,
Pyramids in Egypt, and the Bighorn Medicine Wheel in Wyoming.
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Early Astronomers
Aristotle (383 – 322 B.C.E.) – in 350 BC he provided a scientific explanation of
why the earth is round. He believed the universe was geocentric (planets revolved
around the EARTH). He based his theories on observations he make. He believed
that because patterns of stars in the sky did not change the Earth must be in a
fixed place. If it moved he thought we would see patterns of stars change (page
368). He also believed that because of the shadow created by the Moon during an
eclipse the Earth must be a sphere. (the earth cast shadows with curved edges on
the Moon during an eclipse)
E/A
*Easy strategy to remember – Earth in the middle/ thought Aristotle
- Draw a large G around the circle to represent geocentric
Grade 9 Science
Unit 1/Chapter 10
Ptolemy – AD 150 he published a summary of all that was known about astronomy.
It was used for more than 1,000 years. Ptolemy questioned Aristotle’s model
because it did not explain all the observe motion of the planets. For example, Mar’s
movement (over a period of weeks) is creates a loop or S shape. This is called
retrograde motion.
While observing Mars closely he also developed a model to the solar system
to explain it. His model showed each planet attached to a crystal sphere with its
centre at Earth. Ptolemy thought each planet was attached to an off centered
wheel, which rotated as the sphere turned. This small wheel was called an epicycle.(
a small circle, the center of which moves on the circumference of a larger circle at
whose center is the earth and the circumference of which describes the orbit of
one of the planets around the earth).
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Astrolabe – it was developed around the time of Ptolemy. Astronomers used them
to help locate and predict the positions of the Sun, Moon and stars.
Grade 9 Science
Unit 1/Chapter 10
Copernicus (1473 – 1543) – lived before the telescope was invented. He observed
the sky using just his eyes and suggested that the movement of celestial bodies
that earlier astronomers had observed (the daily rotation of the heavens, the
annual movement of the Sun through the ecliptic, and the periodic retrograde
motion of the planets) could be explained in a simple model in which Earth rotated
on it axis (tilted) once daily and revolved around the Sun once a year. He was very
brave to suggest this because people in his time period believed in the geocentric
model. ** Copernicus’ model of heliocentric universe set the stage for other
scientists to better understand the universe and to propose their own theories
based on his model.
Sun/C
Is this a geocentric or heliocentric model? Should you put G or
H through the circle?
Retrograde Motion – it is the switch in motion of a celestial body form eastward
to westward (or the other) as viewed from Earth. For example, the S shape motion
seen by Mars.
Mars - retrograde motion
Grade 9 Science
Unit 1/Chapter 10
Galielo (1564-1642) – in 1609 he built a telescope based on another model built in
1608. He was the first person to report his use of the telescope for astronomical
use. His telescope was not very strong (it only magnified objects 20 times closer)
but it as powerful enough to let him see a few celestial bodies (Moon, spots on the
Sun and four moons orbiting Jupiter) He figured out that Venus had phases like
our Moon (then it must orbit the Sun) and therefore our universe was a
heliocentric universe. Galileo published his findings. The Catholic Church (Italy)
believed in a geocentric universe and put Galileo on trial for his theory. He was
found guilty and imprisoned for the rest of his life.
G
Sun/
G
*Draw a large H through the
circle to represent heliocentric
Geocentric Universe – believed the EARTH was the center
Heliocentric Universe – belief that the SUN was the centre of the universe. This
theory was proposed by Aristarchus and later strongly supported by Aristotle.
Grade 9 Science
Unit 1/Chapter 10
Telescope – is an optical (sense of sight) device that uses lenses to gather and
focus light to provide a magnified view. The satellites orbiting through space are
large telescopes.
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Kepler – published his 3 laws of planetary motion. Knew about Copernican’s model
and felt he could describe the motions of the planets more accurately and learn
more about the solar system by using new technologies to make very accurate
observations then analyze the date using math.
Newton – in 1687 he linked astronomy with physics. Newton was considered to be
the most influential scientist who ever lived. He describe 3 laws to describe and
predict motion, and explain how celestial bodies move through the universe. Newton
was the first to show mathematically that the force of gravity extend outside of
the earth (think of the visual of Newton sitting under a tree and apple hits him on
the head because of gravity). He use math to show the celestial bodies remain in
orbit around larger bodies because of gravity. The Moon revolves around planets
and planets revolve around the Sun in elliptical orbits. Using Newton’s laws,
scientists calculate how to send people to the Moon and spacecrafts into space. He
also invented the reflecting telescope that was larger and allowed more precise
observations. Newton’s design for this telescope it called the Newtonian design.
Grade 9 Science
Unit 1/Chapter 10
The Scale of the Solar System
Many scientists have contributed to our understanding of the universe. The basic
model that we now use has not changed since Newton’s time. But astronomers have
learned more about the planets and their orbits. We now know…
1. Celestial bodies in the solar system orbit the Sun in elliptical orbits
(oval, egg shaped)
2. Celestial bodies are held in place by _ _ _ _ _ _ _ (I’m not tell you
anymore)
3. planet rotate on their axis which cause day and night (side facing sun
is day)
The Scale
Planets see with the naked eye – Mercury, Venus, Mars, Jupiter and Saturn
Barely visible – Uranus (is very far away and appears to move slowly, some
astronomers thought it was a star)
Cannot be seen with the naked eye – Nepturn (interesting fact – Neptune affects
the gravitation orbit of Uranus. It causes Uranus to have an imperfect eclipse).
Because of this scientists used math to calculate the Neptune even exists.
V
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V–U
NV - N
MVMJS (Can you think of a phrase to remember these letters?)