Outer Space

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The UniversePages 4–5

The SunPages 6–8

MercuryPages 9–11

VenusPages 12–14

Earth and MoonPages 15–17

MarsPages 18–20

JupiterPages 21–23

SaturnPages 24–26

UranusPages 27-29

NeptunePages 30–32

PlutoPages 33–35

CONTENTS

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The StarsPages 36–38

GalaxiesPages 39–40

Black HolesPages 41–42

Manned RocketsPages 47–48

Inside a SpacecraftPages 49–51

SatellitesPages 58–59

Future MissionsPages 60–61

Early RocketsPages 45–46

CONTENTSCelestial BodiesPages 43–44

Moon LandingMissionsPages 52–54

Return to EarthPages 55–57

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Most astronomers think that around fourteen billionyears ago, the universe arrived with a bang! At thattime, the entire universe was inside a bubble that wasthousands of times smaller than a letter on this page. Itwas hotter and denser than anything we can imagine.Then it suddenly exploded, and the universe was born.Nothing existed before this ‘big bang’ – no stars, nospace and no time.

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The universe contains all space and time, all forms ofmatter, energy and momentum. It is so big thatastronomers have to use the distance that light travelsin one year to measure it. They estimate that theuniverse is at least 93 billion light years across! Togive you an idea of how big that is, a beam of lightcan travel from Earth to the Moon in just one second.That's 300,000 km per second! Just imagine how farlight can travel in 93 billion years!

How big is the universe

The universe is a vast, perhaps infinite, mass of galaxies. Older than we canpossibly imagine, it is measured in ‘light years’ due to its phenomenal size.Whether it was formed by a ‘big bang’, or it developed in another way,scientists have created their own theories about the secrets it may hold …

THE UNIVERSE

8 minutes

An artist’s impression of the ‘big bang’

Earth is eight light minutes from the Sun

What was the ‘big bang’

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How far can astronomers see into the universe

With powerfultelescopes, like theHubble pictured below,astronomers can seegalaxies that are overten billion light yearsaway, which means thelight from them hastaken ten billion years toget to Earth. More thanten billion light years is almost the same distance as ahundred billion trillion kilometres!

Astronomers cannot say for certain what lies beyondthis distance. It is impossible to say that the universedefinitely stops or ends somewhere – which means thatit could even go on forever!

A space observatory

The Hubble Space Telescope

There are no certain facts to be had about the pastand future of the universe.

Different scientists have different explanations forthe way things are and do not always agree.

Most believe in a ‘big bang’ theory, others have putforward different theories – what do you think?

FACT FILE

The universe is full of galaxies

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The Sun makes life on our planet possible by giving us great amounts of lightand heat. It is situated at the centre of our solar system and all the planetsand other objects orbit around it. Without the Sun, no living thing would beable to survive and our planet would be completely frozen.

Where did the Sun come from

Five billion years ago, the part of space where oursolar system now exists was full of clouds ofhydrogen gas and dust. Over billions of years, thisgas and dust slowly moved together, due to gravity.As more and more gas and dust came together,nuclear reactions began to take place and the gasstarted to shine!

The Sun orbits the centre of the Milky Way galaxy. Itis made up of around 75 per cent hydrogen and 25per cent helium. It measures more than a millionkilometres across – so big that you could fit morethan 1 million Earths inside it!

THE SUN

At its centre the Sunis an extreme 15million°C – so hotthat planets millionsof kilometres awayreceive its heat! TheSun’s temperatureslowly decreasestowards its surfacewhere it is about6,000°C. This iscool for the Sun, butis actually about 16times hotter thanboiling water! Atthe outermost layer,something strangehappens because thetemperature rises again to well over 1 million°C!

During the first half of the twentieth century, SirArthur Eddington explained that heat and light isgenerated by the Sun when particles called protonscrash into the Sun’s core.

Sir Arthur Eddington

How hot is the Sun

The corona is the outermost layer of the Sun.It stretches millions of kilometres into space.

Believe it or not, the Sun is just a star, just like thosewe see twinkling at night.

FACT FILE

WARNING! The Sunis very dangerous.You should NEVER staredirectly at it or lookthrough a telescope at it.

corona

convective zone

radiative zone

core

sunspot

The Sun

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photosphere

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Sunspots are strange and powerful phenomenon.Sometimes as big as Earth, they move across thesurface of the Sun, shifting in size and shape as theygo. Cooler and darker than surrounding areas of theSun’s surface, sunspots occur when a magnetic field isformed below the Sun's surface.

Enlarged area of the Sun showing a sunspot

What is a sunspot

The seasons in the northern hemisphere. Note the tilt inrelation to the Sun

spring

winter

autumn

summer

We have seasons – spring, summer, autumn andwinter – because Earth is tilted. This tilting causesdifferent parts of the globe to be positioned towardsthe Sun at different times of the year. If the northernhemisphere is tilted towards the Sun, it will be summerthere. At the same time, the southern hemisphere willbe tilted away from the Sun and it will be winter.Autumn and spring occur when Earth is tilted neithertowards or away from the Sun. This means differentsides of the world experience opposite seasons at thesame time.

Why do we have seasons

If you add up all of the mass in the solar system,including the planets, the moons, the asteroids, thecomets, the dust, you and everything else, it turnsout that 99.85 per cent of everything is the Sun.

FACT FILE

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