1. THE SOLAR SYSTEM AND BEYOND
In This Topic We Will Learn About:
The Sun as a star.
The Solar system.
Luminous and non-luminous objects.
A day, a month and a year.
Day and night.
Summer and winter.
Stars and constellations.
Telescopes and beyond the solar system.

2. THE SOLAR SYSTEM AND BEYOND
Our solar system is made up of one star (the Sun), planets, moons and other objects such as asteroids.
The Sun is the only luminous object in our solar system.
Luminous means that it makes its own light.
We can only see the other objects in the solar system because they reflect light from the Sun.
If light from the Sun cannot reach these other objects we will not be able to see them.
Name some other luminous objects.
Light bulbs, fires and stars.
If stars are luminous, why can’t we see them in the daytime?
We cannot see them in the daytime because they are so far away that their light is very dim compared with the light we get from the Sun.

3. The movement of the Earth and our Moon gives us the definitions of:
PLANETS AND MOONS
The planets, moons and asteroids in our solar system are always moving.
The stars seem to move too.
Astronomers have watched the movement of the stars, moons and planets for thousands of years.
They have used these movements to measure time.
The movement of the Earth and our Moon gives us the definitions of:
One day:
The time it takes for the Earth to spin around once on its axis.
One month:
The time it takes the Moon to orbit the Earth once.
One year:
The time it takes the Earth to orbit the Sun once.

4. THE SOLAR SYSTEM AND BEYOND
The Earth is always spinning on its axis.
It takes one day for the Earth to turn around completely.
For part of this time our side of the Earth will be facing the Sun.
Light and heat from the Sun will reach us.
It will be day time.
What happens when our side of the Earth is not facing the Sun?
Light and heat from the Sun will not be able to reach us.
It will be night time.
Earth spins
on its axis
night
day

5. RISING AND SETTING OF THE SUN
Because the Earth is always spinning, we keep looking at the Sun from different angles.
This makes it look as if the Sun is moving across the sky.
It is really we (the Earth) who are moving.
The Sun seems to move from the east, through the south, towards the west.
Midday –
The Sun is
overhead.
Morning-
The Sun rises
in the east.
Evening-
The Sun sets in the west.

6. THE YEAR AND SEASONS
It takes one year for the Earth to orbit the Sun once.
Because the Earth’s axis is tilted, the northern hemisphere points towards the Sun for part of the year and away from the Sun for part of the year.
Summer
Winter
During which season is our hemisphere pointed towards the Sun?
Summer.
What season is it in the southern hemisphere at this time?
Winter. When the northern hemisphere points towards the Sun, the southern hemisphere will be pointing away from the Sun.
When is the Earth closest to the Sun?
Spring and Autumn.

7. A LUNAR MONTH
While the Earth is spinning on its axis and travelling in orbit around the Sun, the Moon is orbiting the Earth.
It takes the Moon 28 days (one lunar month) to orbit the Earth once.
Because the Moon is moving around the Earth, we see the Moon from different angles at different times of the month.
When we see the Moon, we are seeing light reflected from the part of the moon that is facing the Sun.
We see different amounts of this part of the moon at different times
This is why the shape of the moon seems to change (the phases of the Moon).

8. HOW DO PHASES OF THE MOON WORK?
The Moon does not make its own light.
We can only see the Moon because it reflects light from the Sun.
Light from the Sun always gets to half of the Moon but, because the Moon is moving around the Earth, we cannot always see this half.
In the UK, we will not be able to see
much of the half of the moon that is lit
up by the Sun.
We will see a thin crescent moon.
In the UK, we will be able to see most
of the half of the Moon that is lit up by
the Sun.
We will see an almost full moon.

9. THE SOLAR SYSTEM
There are nine planets orbiting the Sun in our solar system.
The asteroids orbit between the inner planets and the outer planets.
Key: Inner planets
Outer planets
Asteroid belt
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto

10. DATA FOR THE SOLAR SYSTEM
Planet
Distance from the Sun
(millions of km)
Time to orbit the Sun once
(length of year)
Surface temperature
( ºC)
Mercury 60
88 days
170
Venus
110
225 days
460
Earth
150
365 days 15
Mars
230
687 days
-50
Jupiter
780
12 years
-140
Saturn
1430
29 years
-195
Uranus
2870
84 years
-200
Neptune
4500
165 years
-220
Pluto
5900
248 years
The different planets have different features
They have different surface temperatures and take different lengths of time to orbit the Sun once.
Why do the more distant planets take longer to orbit the Sun?
They have further to travel.
What is the link between temperature and distance from the Sun?
The closer the planet is to the Sun, the hotter it is.
Which planets do not fit this pattern?
Venus and Pluto.

11. TELESCOPES
We can see some planets with the ‘naked eye’. Astronomers have known about these planets for thousands of years.
More distant planets were only discovered in the last few hundred years.
What discovery enabled astronomers to find out about more distant planets such as Pluto?
The telescope.
What developments have happened in the last 50 years or so that have helped us find out even more about the Moon, stars and the planets?
Radio telescopes.
Space exploration – both manned and unmanned.

12. CONSTELLATIONS There are millions of stars in the universe.
Stars are grouped together in galaxies.
There are millions of galaxies.
Every galaxy contains millions of stars.
Our Sun is part of the Milky Way galaxy.
Constellations are groups of stars that seem to form a pattern, for example ‘the Plough’.

13. STARS AND GALAXIES
Stars and galaxies are too far away to be visited by space probes and rockets. It would take thousands of years to reach even the nearest star.
We can see millions of stars with the naked eye.
Telescopes let us see some details of the stars nearest to us.
Radio telescopes are usually used to investigate stars and galaxies thoroughly

14. Space Objects Which of these space objects do you recognise?
What do you know about them?

15. A comet – a head of ice and a tail of gas. Comets orbit the Sun.
Answers
A constellation –
a group of stars
that seem to make
a pattern in the sky.
A comet – a head of ice and a tail of gas. Comets orbit the Sun.
A galaxy – millions
of stars grouped
together.
Saturn – the
second largest
planet in our
solar system.
Asteroids in the
asteroid belt –
minor planets
that orbit the Sun
between Mars and
Jupiter.
Jupiter – the
largest planet
in our solar
system.
Our moon- orbits
the Earth once
every 28 days.
The Earth – the third planet
from the Sun.