Outer Space
Copyright Š 2010 Top That! Publishing plc Tide Mill Way, Woodbridge, Suffolk, IP12 1AP, UK www.topthatpublishing.com Top That! is a trademark of Top That! Publishing plc All rights reserved
CONTENTS The Universe Pages 4–5
The Sun Pages 6–8
Mercury Pages 9–11
Venus Pages 12–14
Earth and Moon Pages 15–17
Mars Pages 18–20
Jupiter Pages 21–23
Saturn Pages 24–26
Uranus Pages 27-29
Neptune Pages 30–32
Pluto Pages 33–35
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CONTENTS The Stars Pages 36–38
Galaxies Pages 39–40
Black Holes Pages 41–42
Early Rockets Pages 45–46
Manned Rockets Pages 47–48
Inside a Spacecraft Pages 49–51
Moon Landing Missions Pages 52–54
Return to Earth Pages 55–57
Satellites Pages 58–59
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Celestial Bodies Pages 43–44
Future Missions Pages 60–61
THE UNIVERSE The universe is a vast, perhaps infinite, mass of galaxies. Older than we can possibly 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 …
How big is the universe The universe contains all space and time, all forms of matter, energy and momentum. It is so big that astronomers have to use the distance that light travels in one year to measure it. They estimate that the universe is at least 93 billion light years across! To give you an idea of how big that is, a beam of light can travel from Earth to the Moon in just one second. That's 300,000 km per second! Just imagine how far light can travel in 93 billion years!
8 minutes
Earth is eight light minutes from the Sun
What was the ‘big bang’ Most astronomers think that around fourteen billion years ago, the universe arrived with a bang! At that time, the entire universe was inside a bubble that was thousands of times smaller than a letter on this page. It was 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, no space and no time.
An artist’s impression of the ‘big bang’
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How far can astronomers see into the universe With powerful telescopes, like the Hubble pictured below, astronomers can see galaxies that are over ten billion light years away, which means the light from them has taken ten billion years to A space observatory get to Earth. More than ten billion light years is almost the same distance as a hundred billion trillion kilometres! Astronomers cannot say for certain what lies beyond this distance. It is impossible to say that the universe definitely stops or ends somewhere – which means that it could even go on forever!
The universe is full of galaxies
FACT FILE There are no certain facts to be had about the past and future of the universe. Different scientists have different explanations for the way things are and do not always agree. Most believe in a ‘big bang’ theory, others have put forward different theories – what do you think?
The Hubble Space Telescope
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THE SUN The Sun makes life on our planet possible by giving us great amounts of light and heat. It is situated at the centre of our solar system and all the planets and other objects orbit around it. Without the Sun, no living thing would be able to survive and our planet would be completely frozen.
Where did the Sun come from
How hot is the Sun
Five billion years ago, the part of space where our solar system now exists was full of clouds of hydrogen gas and dust. Over billions of years, this gas 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 gas started to shine!
At its centre the Sun is an extreme 15 million°C – so hot that planets millions of kilometres away receive its heat! The Sun’s temperature slowly decreases towards its surface where it is about 6,000°C. This is cool for the Sun, but is actually about 16 times hotter than boiling water! At the outermost layer, something strange Sir Arthur Eddington happens because the temperature rises again to well over 1 million°C!
The Sun orbits the centre of the Milky Way galaxy. It is made up of around 75 per cent hydrogen and 25 per cent helium. It measures more than a million kilometres across – so big that you could fit more than 1 million Earths inside it!
FACT FILE The corona is the outermost layer of the Sun. It stretches millions of kilometres into space.
During the first half of the twentieth century, Sir Arthur Eddington explained that heat and light is generated by the Sun when particles called protons crash into the Sun’s core.
Believe it or not, the Sun is just a star, just like those we see twinkling at night.
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photosphere
corona convective zone
radiative zone
core
sunspot WARNING! The Sun is very dangerous. You should NEVER stare directly at it or look through a telescope at it.
The Sun
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Why do we have seasons
What is a sunspot Sunspots are strange and powerful phenomenon. Sometimes as big as Earth, they move across the surface of the Sun, shifting in size and shape as they go. Cooler and darker than surrounding areas of the Sun’s surface, sunspots occur when a magnetic field is formed below the Sun's surface.
We have seasons – spring, summer, autumn and winter – because Earth is tilted. This tilting causes different parts of the globe to be positioned towards the Sun at different times of the year. If the northern hemisphere is tilted towards the Sun, it will be summer there. At the same time, the southern hemisphere will be tilted away from the Sun and it will be winter. Autumn and spring occur when Earth is tilted neither towards or away from the Sun. This means different sides of the world experience opposite seasons at the same time.
spring
summer
winter
Enlarged area of the Sun showing a sunspot
FACT FILE If you add up all of the mass in the solar system, including the planets, the moons, the asteroids, the comets, the dust, you and everything else, it turns out that 99.85 per cent of everything is the Sun.
autumn
The seasons in the northern hemisphere. Note the tilt in relation to the Sun
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