Discovering Planets & Moons

Discovering Planets & Moons book cover — TABLE OF CONTENTS INTRODUCTION 5 PLANETS 8 MOONS 24 GALAXIES 42 STARS 50 DWARF PLANETS 60 SPACE TECHNOLOGY 68 SUPERLATIVES 76 INDEX 84

Discovering Planets & Moons — page 1 — The Earth and Sun as seen from space 4

Discovering Planets & Moons — page 2 — INTRODUCTION It’s hard to imagine what is beyond our planet but in reality the universe is much bigger than life on Earth Looking up at the sky can tell us a lot about the universe and ancient astronomers did just that as they started exploring space During the day the Sun and clouds show just a hint of what’s beyond Earth but at night the Moon and stars show us that there is far more out there than first meets the eye The invention of the telescope in the early 1600s gave us a new way to look at the sky Astronomers could see much farther into space far beyond what merely their eyes could see They mapped and calculated and spent years trying to learn more about space In the 1960s we made another huge stride in space exploration by sending humans into outer space To investigate what lies beyond our world humans have studied the Moon and stars from spaceships walked on the Moon and even lived in outer space in the International Space Station page 73 WHAT IS IN SPACE Once you leave planet Earth there is no breathable air in the atmosphere That’s why astronauts have to wear large oxygen tanks when they are outside of their spaceship Outer space is black but that doesn’t mean it’s empty Gas dust and matter make up most of space but there are also objects like planets page 9 moons page 25 galaxies page 43 stars page 51 and dwarf planets page 61 There are also smaller objects like meteors asteroids and comets that move throughout space Two interesting elements of space are supernovas and black holes When a star runs out of fuel it explodes this explosion forms a supernova Black holes are areas where nothing not even light can escape from These mysteries of space are hard to understand because scientists have not been able to explore them Objects in space are not stationary most travel in an orbit around another object Sometimes these moving objects collide It’s impossible for us to measure the size and age of space Our explorations have led us to find objects that are billions of years old Distance in space is measured in light years or the distance that light travels in one year Despite all of our explorations we have not yet found evidence of other forms of life in space 5

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