Transcript Intro to Astronomy

Intro to Astronomy
Grade 9 Science
Astronomy Intro
Grade 9 Science
• The universe is
everything that
exists, including all
matter and energy
everywhere.
• The study of what
is beyond Earth is
called astronomy.
Astronomy Intro
Grade 9 Science
History…
Geocentric Model
• The geocentric model (earth
centered model) was based on an
ideas from Aristotle, but refined and
finished by Claudius Ptolemy.
• Ptolemy imagined that the solar
system was made of perfect circles,
but his model also had to explain
retrograde motion. He did this by
adding smaller perfect circles
(epicycles) on the orbital paths of
each planet (except for the sun).
Astronomy Intro
Grade 9 Science
Heliocentric Model
• Nicholas Copernicus with the
help of Galileo proposed a
model where the sun is the
center of solar system. This
model was not well received,
but it did explain the retrograde
motion better then Ptolemy’s
model.
• Johannes Kepler added to
Copernicus’s by changing the
orbital paths to elliptical instead
of circular. This explained the
speed changes they observed
in the night sky.
Astronomy Intro
Grade 9 Science
Origins of the Universe
• There are a lot of models and ideas that
exist to explain how the universe came
about. The current accepted scientific
model is called the Big Bang theory.
Which states that the universe started
from an infinitesimal point that exploded
in a huge release of energy and matter
10 to 15 billion years ago.
• The study of the origin and changes of
the universe is called cosmology.
Astronomy Intro
Grade 9 Science
• Planets orbit the sun in elliptical orbits which are caused
by gravitational forces. Orbital Period is the time it
takes for one full orbit. Orbital period increases as the
body gets closer to the sun. Along with orbiting, a
planet also rotates about a central axis.
Astronomy Intro
Grade 9 Science
Planets have two types of motion:
Rotation
Revolution
Effect of Earth’s Rotation
• Rotation – the spinning of an object around its
axis (an imaginary straight line joining the North
Pole to the South Pole)
• The Earth’s rotation around its axis takes 24
hours. The rotation causes day and night.
Astronomy Intro
Grade 9 Science
Effect of Earth’s Revolution
• Revolution – the movement of one object
travelling around another.
• It takes the Earth one year (365 days) to
revolve around the Sun. This allows us to
see different stars in different seasons.
• The angle of the Earth’s axis in
combination with its revolution cause our
seasons.
Astronomy Intro
Grade 9 Science
Seasons
• Although the Earth’s distance from the Sun
changes slightly as it orbits, the distance is not
great enough to cause a substantial change in
the climate.
• The tilt of the Earth (23.5o) is what causes the
seasons to change.
• During the summer, the Northern Hemisphere is
titled towards the Sun, while during the winter
the Northern Hemisphere is titled away from the
Sun.
Astronomy Intro
Grade 9 Science
• Each planet is unique in our solar system.
Some of the differences are:
–
–
–
–
Surface temperature
Density
Combination of chemical elements
Gravitational field strength
Astronomy Intro
Grade 9 Science
The Inner Planets (Terrestrial Planets)
• 1. Mercury
• 2. Venus
• 3. Earth
• 4. Mars
The Outer Planets (Gas Giants)
• 1. Jupiter
• 2. Saturn
• 3. Uranus
• 4. Neptune
• 5. Pluto (Dwarf Planet)
Mercury
Diameter:4,878km
Mass:0.0553EM
Density:5.43
Gravity:0.284EG
Average Temperature:
400 to -170°C
Venus
Diameter:12,102km
Mass:0.8149EM
Density:5.25
Gravity:0.878EG
Average
Temperature:500°C
Earth
Diameter:12,756km
Mass:5.9741024 kg
Density:5.52
Gravity:9.8m/sec2
Average
Temperature:15°C
Mars
Diameter:6,786km
Mass:0.1074EM
Density:3.95
Gravity:0.379EG
Average Temperature: 60°C
Jupiter
Diameter:142,984km
Mass:317.938EM
Density:1.33
Gravity:2.4EG
Average Temperature: 140°C
Saturn
Diameter:120,536km
Mass:95.181EM
Density:0.69
Gravity:0.923EG
Average Temperature:
-175°C
Uranus
Diameter:51,118km
Mass:14.531EM
Density:1.29
Gravity:0.793EG
Average Temperature: 214°C
Neptune
Diameter:49,528km
Mass:17,135EM
Density:1.64
Gravity:1.122EG
Average
Temperature:-214°C
Astronomy Intro
Grade 9 Science
Solar System
• At the centre of
our solar system
is a star, the Sun,
that is essential to
life on Earth. The
sun is the largest
body in our solar
system.
Astronomy Intro
Grade 9 Science