Table of Contents Introduction 4 The Sun 8 The Active Sun 12 Birth and Death of the Sun 16 The Sun and Life 20 Studying the Sun 26 Light Shows 28 Planets 32 Mercury 36 Venus 38 Earth 40 Mars 42 Jupiter 44 Saturn 46 Uranus 48 Neptune 50 Dwarf Planets 52 Exoplanets 56 The Moon 58 What the Moon Is Made Of 60 Birth of the Moon 64 Moon Phases 66 The Moon’s Effects on Earth 70 Space Exploration 78 The Space Race 82 Exploring the Solar System 88 Space Stations 96 Shuttling into Space 102 Space Tourism 108 Asteroids Comets and Meteoroids 112 The Solar System’s Leftovers 114 When Meteorites Land 118 Fear of Falling Objects 122 Famous Asteroids and Comets 126
Stars 132 A Star Is Born 134 Stars of Many Colors 136 Constellations 144 Notable Stars 148 The Universe 172 The Big Bang 174 The Observable Universe 176 Dark Energy and Dark Matter 178 The Multiverse 184 Galaxies 150 The Early Galaxy 152 The Size and Shape of the Milky Way 156 Galaxy Diversity 160 Discovering More Galaxies 164 The Andromeda Collision 168 Galaxy Clusters 170 Conclusion 186 Glossary 188 To Learn More 189 Index 190 Photo Credits 191
Introduction For thousands of years human cultures have had a deep interest in the skies above them The motions of objects in the sky told the people of North America many things These things included when to plant when to harvest when to hunt and when to celebrate Researchers think England’s Stonehenge structure was a temple designed to follow the sun’s movements In Africa a stone circle built 7,000 years ago tracked the summer solstice and the arrival of the rainy season Many cultures saw gods and goddesses moral lessons and hints of things to come in the night sky As humans learned People began building Stonehenge thousands of years ago 4
In this diagram the blue line represents the Kármán line The red line shows the altitude of a space station about 250 miles 400 km above the surface more about the natural world they began to discover the scientific nature of the things they saw in the sky There is no distinct boundary above Earth where space begins The atmosphere gradually becomes thinner and thinner as the altitude increases But one commonly accepted point for this transition is the Kármán line Named for scientist Theodore von Kármán it is located at an altitude of 62 miles 100 km above the planet’s surface 5
