1. The Planets and the Solar System
Where we’re going today…
• Solar System
By the end of this class, you should be able to…
Define planet and solar system.
Describe the difference between rotation and revolution. What does each movement cause?
Describe the difference between the inner planets and the outer planets.
Briefly describe all the planets.

2. The Planets and the Solar System
Planet – is a celestial body that orbits one or more stars.
Planets only reflect light radiated by its star, they do NOT generate their own energy.
Solar System – a group of planets circling one or more stars
Each galaxy spins around a central nucleus.
Within our spinning galaxy (Milky Way) our solar system is also rotating (250 km/s)
Within our solar system, all the planets are in motion too, including Earth…
…around itself and around the sun…

3. The Planets and the Solar System
…around itself…
Rotation- motion of a planet
as it spins on its axis
(imaginary line from north
to south)
Earth moves from west to east
at 1670 km/h or 0.5 km/s
…around the sun…
Revolution – motion of a planet
as it orbits the Sun (Earth = 30 km/s)
The Earth and other planets follow
an elliptical path around the Sun.

4. The Planets and the Solar System
The Formation of the Solar System
Our solar system was formed more than 4.5 billion years ago.
Left over material from our Sun’s formation combined to form eight planets and numerous other smaller bodies (moons, asteroids, comets)
Not all the planets formed at the same time or in the same way…

5. The Planets and the Solar System
In the first 100 million years or so, the material closest to the young Sun developed into planets – Mercury, Venus, Earth and Mars.
These are called the inner planets or terrestrial (Earth-like) planets
They have
relatively
small, solid
cores and
rocky
crusts

6. The Planets and the Solar System
Further away, large clumps of gas, ice and dust formed Jupiter, Saturn, Uranus and Neptune.
These are called the outer planets or jovian planets
They have large gaseous bands and cold temperatures
The inner and
outer planets are
separated by an
asteroid belt

7. The Planets and the Solar System

9. The Planets and the Solar System
A planet is…
…a body that orbits one or more stars
…large enough that its own gravity holds it in a spherical shape
…the only body occupying its orbital path
Planets are very far apart. So far that we don’t use km’s, astronomers have devised another unit.
Astronomical Unit (AU)
It is equal to the average distance between the Sun and Earth (150 million km)
Therefore the Earth is 1 AU from the Sun

10. The Planets and the Solar System
Mercury
⅓ the size of the Earth
(slightly larger than the moon)
No significant atmosphere
Experiences extraordinary
temperature differences
(night (-143°C) to day (400°C))
Temp differences causes rock to form immense cracks
(due to hot/cold)

11. The Planets and the Solar System
Venus
Similar in size and composition
to Earth (sister planet)
Atmosphere is different
(completely CO2)
Thick clouds cover the planet.
(Sulphur mixes to from acid rain)

12. The Planets and the Solar System
Earth
Only place known to have
water in three phases
(liquid, solid, and gas)
Water covers nearly
three-quarters of the
Earth’s surface
Atmosphere is composed
mainly of N and O

13. The Planets and the Solar System
Mars
Called the red planet
(Fe in its surface)
Half the size of Earth
but same amount of
surface area
(volcanoes and
deep canyons)
Very thin atmosphere of CO2 and winds of more than 900km/h

14. The Planets and the Solar System
Jupiter
Largest planet in the
solar system
(mass about 2.5 times
greater than all other
planets combined)
Has a “great red spot”
the size of three Earths that is a storm raging in the clouds
Composed mainly of H and He
Despite size, Jupiter has the shortest day of all planets (10 hours)

15. The Planets and the Solar System
Saturn
Elaborate system of rings
(formed from ice particles
and dust)
Rings are km
wide & as thin as 10 m
Composed mainly of H and He

16. The Planets and the Solar System
Uranus
Fourth most massive planet
Similar composition to
Jupiter and Saturn
Includes a ring system
composed of ice and dust
Blue colour comes from
methane gas in atmosphere
Unusual rotation – flipped on its side (appears to roll through orbit)

17. The Planets and the Solar System
Neptune
Outermost planet
(third most massive)
Composition similar to
that of Uranus and
same dark blue colour
Has a ring system like
other three gas giants
Has large, blue, earth like patch – likely a storm in the clouds of Neptune (like the red spot of Jupiter)

18. The Planets and the Solar System
Did we get there…
Can you…
Define planet and solar system.
Describe the difference between rotation and revolution. What does each movement cause?
Describe the difference between the inner planets and the outer planets.
Briefly describe all the planets.
Assignment: Planet Profile