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The Earth and Beyond
The Solar System
The Universe
The Solar System - Our Sun
The SOLAR SYSTEM is the SUN and all of its SATELLITES.
The Sun is a STAR. It gives out LIGHT and HEAT due to
NUCLEAR REACTIONS.
Our Sun is made up mainly of the elements HYDROGEN and
HELIUM, but not all stars are the same. There are many
different types with varying SIZES, COLOURS and
TEMPERATURES.
The satellites of the Sun all ORBIT
the Sun because of the Sun’s
GRAVITY. The Sun is the MOST
MASSIVE object in the Solar System.
You should never LOOK at the Sun
DIRECTLY as it could damage
your eyesight permanently!
There are many types
of stars.
The System of Sol
Pluto
Can you name them?
(Not to scale!)
Uranus
Neptune
Jupiter
Saturn
Earth
Mars
Venus
Mercury
The Planets
There are NINE planets in our Solar System. The planets are
kept in orbit by a combination of the SUN’S GRAVITY and their
SPEED. The Earth takes 365.25 DAYS for one orbit of the Sun.
Unlike the Sun, the planets are seen by REFLECTED LIGHT.
They move around the Sun, not in circular orbits, but in slightly
squashed orbits – ELLIPTICAL ORBITS.
The first four planets, the
INNER PLANETS, are
SMALL and ROCKY:
The next four planets, the
OUTER PLANETS, are
LARGE and GASEOUS:
MERCURY
JUPITER
VENUS
EARTH
MARS
What about
Pluto?
SATURN
URANUS
NEPTUNE
The Planets
There are nine planets in the Solar System. The planets
orbit (orbit means to move around in a path) the Sun in
slightly elliptical orbits.
The planets are similar in some ways, but in others are
very different.
By looking at each of the planets in turn you can build up
a picture of the Solar System as a whole.
Mercury
Relative mass:
0.06
Diameter:
4 879
Distance from Sun (million km):
57.9
Orbital period:
Moons:
88 days
None
Mercury is the closest planet to the Sun. In appearance
and size Mercury is very similar to the Moon. Mercury, like the
Moon, has a cratered appearance.
Mercury has an elliptical orbit and is the second smallest
planet after Pluto. During the day the temperature on Mercury
reaches 450°Celsius. During the night, due to the lack of
atmosphere, the temperature falls to –180°Celsius.
These harsh conditions mean that it is unlikely there is life
on Mercury.
Venus
Relative mass:
0.82
Diameter:
12 104
Distance from Sun (million km):
108.2
Orbital period:
Moons:
224.7 days
None
Venus is the second planet moving out from the Sun.
Venus is covered in thick clouds as seen from Earth. We have
been able to study the surface of Venus using radar mapping.
Venus would not be a nice place to visit. It has a surface
temperature higher than that of Mercury. This is caused by the
‘Greenhouse Effect’ of the dense Venusian atmosphere
which consists mainly of carbon dioxide.
If you stood on the surface of Venus you would be
incinerated by the high temperatures, corroded by the
sulfuric acid found in the atmosphere, suffocated by the lack
of oxygen and crushed by the dense atmosphere.
Earth
Relative mass:
1
Diameter:
12 756
Distance from Sun (million km):
149.6
Orbital period:
Moons:
365.3 days
1
The Earth is the third planet from the Sun. It has a surface
covered 70% by liquid water and the rest by rock. It has an
atmosphere that consists mainly of nitrogen and oxygen. It
is also the only place in the Solar System where life is
known to exist.
The Earth spins once on its axis every 24 hours. This
causes day and night on Earth.
The Earth is tilted on its axis. It is this tilt that causes the
Seasons.
It takes the Earth 365.3 days to orbit the Sun once.
Mars
Relative mass:
0.11
Diameter:
6 796
Distance from Sun (million km):
227.9
Orbital period:
Moons:
687.0 days
2
Mars is the fourth planet from the Sun. Like Mercury, Venus
and Earth, Mars is small and rocky. Together these four planets
make up the four inner planets. Mars is often referred to as the
‘Red Planet’. This is because it is covered in red dust on the
surface of the planet.
It was once thought that there was life on Mars. Spacecraft have
visited Mars but life has not yet been detected. There is evidence
liquid water once flowed on Mars. Liquid water is a requirement
for life as we know it. Even though there may be no life on Mars
now, there may have been life on Mars in the past.
Mars has two moons, Phobos and Deimos. They are thought
to be captured asteroids.
Jupiter
Relative mass:
Diameter:
Distance from Sun (million km):
Orbital period:
Moons:
318
143 884
778.3
11.9 years
16
Jupiter is the largest planet in the Solar System. If Jupiter
had been eight times more massive then it would not have
formed a planet, it would have formed a star.
Jupiter does not have a solid surface but is a gaseous
planet. Jupiter is famous for its ‘Red Spot’; this is a large
storm in Jupiter’s upper atmosphere that is three times bigger
than Earth!
Jupiter has 16 moons. The four largest are Io, Europa,
Ganymede and Callisto. Europa is thought to possess liquid
water and it is possible that it could support life.
Saturn
Relative mass:
95
Diameter:
120 536
Distance from Sun (million km):
1 427.0
Orbital period:
Moons:
29.5 years
8 major, several minor
Saturn is the sixth planet from the Sun and is gaseous
in nature. Saturn is famous for its beautiful ring-system.
The rings are not solid but are thought to consist of
millions of particles of ice.
Saturn, like Jupiter, consists mainly of the elements
Hydrogen and Helium. Saturn has an overall density that is
less than the density of water. This means that if you could find
a sea large enough, then the planet Saturn would float.
Will Hay, the famous British comedian, was a keen amateur
astronomer who discovered a ‘White Spot’ upon the surface of
Saturn.
Uranus
Relative mass:
15
Diameter:
50 724
Distance from Sun (million km):
2 869.6
Orbital period:
84.0 years
Moons:
15
Uranus is the seventh planet from the Sun and is
gaseous in nature. Uranus also has a ring-system similar
to Saturn. However, the rings of Uranus are thought to
consist of dust from the break-up of a moon; perhaps
caused by an asteroid collision.
Uranus is barely visible to the naked eye and was
unknown to ancient peoples. It is clearly visible with a
small telescope and has 15 moons. Only five of the moons
are visible from Earth – Miranda, Ariel, Umbriel, Titania
and Oberon.
Neptune
Relative mass:
17
Diameter:
50 538
Distance from Sun (million km):
4 496.7
Orbital period:
Moons:
164.8 years
8
Neptune is the eighth planet from the Sun, although for
part of its orbit Neptune is the furthest planet from the Sun.
Neptune is the fourth gas giant (along with Jupiter, Saturn
and Uranus).
Neptune has a ring-system and an active cloud-system.
The winds on Neptune are thought to reach up to 2 000
kilometres per hour – that is faster than a bullet!
One of Neptune’s eight moons, Triton, is unusual. Triton
is the only moon of a planet that orbits in a direction
opposite to the direction of the planet’s rotation.
Pluto
Relative mass:
0.01
Diameter:
2 445
Distance from Sun (million km):
5 900
Orbital period:
Moons:
247.7 years
1
Pluto is the ninth planet from the Sun. It was only
discovered in 1930 by Clyde Tombaugh. Indeed it was only
in 1978 that it was discovered that Pluto has a solitary moon.
The moon of Pluto is called Charon.
Pluto does not fit the pattern of planets in the Solar
System. It is thought to consist of rock and ice. Pluto also has
a very elliptical orbit (which is why Neptune is sometimes
the furthest planet from the Sun). Some astronomers do not
think Pluto is a true planet and is more similar to an asteroid
or comet.
Exercise 2: The Inner Solar System
1. Which two elements make up most of our local star?
Hydrogen and helium.
2. Why should you never look directly at the Sun?
It could permanently damage your eyesight.
3. How many planets are small and rocky?
Four – Mercury, Venus, Earth and Mars.
4. What do we call these small and rocky planets?
The inner planets.
5. Which planet is closest to the Sun?
Mercury.
6. Which of these planets supports life?
Earth.
Exercise 3: The Outer Solar System
1. Name the four outer planets.
Jupiter, Saturn, Uranus and Neptune.
2. Which is the largest of these four planets?
Jupiter.
3. Name two differences between the inner planets and the outer
planets?
The inner planets are smaller, rocky, have shorter orbital
times and are warmer than the outer planets which are
larger, gaseous, have longer orbital times and are cooler.
4. Which outer planet has a spectacular ring system?
Saturn.
5. Which planet is furthest from the Sun for most of its orbit?
Pluto.
Exercise 5: Temperatures
1. Look at the table and graph. What pattern do you notice?
What is the exception?
Temp. (°C)
Mercury
350
Venus
480
Earth
20
Mars
-23
Jupiter
-150
Saturn
-180
Uranus
-210
Neptune
-220
Average planetary temperatures (in order
from the Sun)
600
500
400
Temperature/ deg C
Planet
300
200
100
0
Mercury
Venus
Earth
Mars
Jupiter
-100
-200
-300
Pluto
-230
Planet
Saturn
Uranus
Neptune
Pluto
Planet Temperatures
As you MOVE FURTHER AWAY FROM THE SUN, THE
TEMPERATURE OF THE PLANETS DECREASES. This is because
they receive less heat energy from the Sun, the further away you get.
Some planets have an ATMOSPHERE. This can affect the
temperature of the planet.
This is why VENUS is HOTTER than MERCURY even though Venus
is FURTHER AWAY FROM THE SUN.
Venus has an atmosphere that contains
GREENHOUSE GASES, they let the
Sun’s heat energy in, but will not let it
escape; the planet gets warmer as a
result. The GREENHOUSE EFFECT.
The surface of Venus is hot enough to
melt LEAD!
The surface of Venus is
shrouded in thick cloud
Exercise 6: Orbital Time
1. Use the data below to draw a graph showing how the orbital
time of a planet varies with its distance from the Sun. What
general pattern can you see?
Planet
Solar Distance
(Millions of km)
Orbital time
(Earth years)
Mercury
58
0.24
Venus
108
0.62
Earth
150
1.00
Mars
228
1.88
Jupiter
779
11.86
Saturn
1430
29.46
Uranus
2870
84.01
Neptune
4496
164.80
Pluto
5906
247.00
Orbital Times
As you MOVE FURTHER AWAY FROM THE SUN, THE
ORBITAL TIME OF THE PLANETS INCREASES. This is
because the further away a planet is, the greater the distance
it must travel to complete one orbit.
Remember, the planets’ orbits are ELLIPTICAL not CIRCULAR.
An interesting point to note is that
even though we say that PLUTO
is the planet that is FURTHEST
AWAY FROM THE SUN, this is
not always TRUE. The orbit of
NEPTUNE is partly outside that of
Pluto. So, for part of its orbit,
NEPTUNE IS THE PLANET
FURTHEST AWAY FROM THE
SUN.
Neptune’s
orbit
Pluto’s
orbit
Moons
MOONS are the NATURAL
SATELLITES of planets. The
natural satellite of the Earth is
THE MOON.
Not all planets have moons.
Some planets have one or two,
and some planets have lots.
Many moons have
craters. Why?
Our moon is barren and lifeless. Some moons in the Solar
System are thought to hold the best chance of finding LIFE;
even if it is in primitive form.
EUROPA is a moon of JUPITER. Europa is thought to
possess LIQUID WATER underneath its icy surface. Liquid
water is a requirement for life as we know it, so many
scientists feel the BEST CHANCE of finding life in our Solar
System is on Europa.
Comets
Comets are objects that orbit the Sun in HIGHLY-ELLIPTICAL
orbits. They are only seen for a SHORT TIME when they are
RELATIVELY CLOSE TO THE SUN. Like Planets and moons,
comets are seen by REFLECTED LIGHT.
Comets are thought to consist of ICE and DUST particles (like a
dirty snowball). It was only recently that we discovered the truth
about comets when several spacecraft flew close to approaching
comets; one craft even passed through the tail of a comet.
HALLEY’S COMET is a famous comet that has an orbital period
of 76 YEARS. Very few people see Halley’s comet twice in their
life and no one ever sees it three times.
What is the tail of a comet?
Evaporating ice particles as the
comet approaches the Sun.
Asteroids
Between the planets MARS and JUPITER thousands of lumps
of rock are found. These lumps or rock are called
ASTEROIDS. The region where they are found is known as
the ASTEROID BELT.
These asteroids have varying and eccentric orbital paths.
Some have passed very close to the Earth; in the past some
have hit the Earth. Some scientists believe that LARGE
ASTEROIDS IMPACTING on EARTH have resulted in MASS
EXTINCTIONS in the past.
There are several large IMPACT CRATERS on the surface of
the Earth thought to have been caused by impacting craters.
The Moon has a lot more visible craters than the Earth
because the Moon has NO ATMOSPHERE to protect it.
Exercise 7: Moons, Comets and Asteroids
1. What do we call the natural satellites of planets?
Moons.
2. Why can we only see comets for a short period of their orbit?
They have highly-elliptical orbits, so for much of their orbit they
are in the outer Solar System and too far away to see.
3. What makes up the tail of a comet?
Evaporated ice particles as the comet approaches the Sun.
4. Where is the asteroid belt found?
Between Mars and Jupiter.
5. How do we see comets, moons and asteroids?
By reflected light.
The Scale of Things
We live on a PLANET
called EARTH.
The Earth and all the planets
ORBIT the SUN.
Our Sun is one of many STARS.
MILLIONS OF STARS grouped
together are called a GALAXY.
Our Sun is part of a SPIRAL
GALAXY called the MILKY WAY.
There are MILLIONS OF
GALAXIES, all the galaxies together
make up the UNIVERSE.
A spiral galaxy
Exercise 8: Scale of the Universe
Our Sun is a _____.
star There are many different types
of star. _______
Millions of star grouped together are called a
_______.
galaxy Our local galaxy is the Milky Way. The
distances between the stars in a galaxy are a lot
planets in our
bigger then the distances between the ______
Solar System.
There are millions of galaxies; together they make up
the ________.
Universe The distances between galaxies in the
Universe is a lot bigger than the distances between
stars in a galaxy.
galaxy
Universe
planets
star millions
Exercise 10: Match the Names with the Body
The Sun
A moon
Europa
A spiral galaxy
Saturn
A star
The Milky Way
A planet
Exercise 9: Which…
1. For the following bodies answer the questions below.
Galaxy
Saturn
Asteroid
Comet
Sun
North Star
a) Which are seen by reflected light?
Saturn, asteroid, comet
b) Which are light sources?
Galaxy, Sun, North Star
c) Which are part of our Solar System?
Saturn, asteroid, comet, Sun
d) Which two are stars?
Sun, North Star