The Sun and Stars

The Sun and Stars — page 1
4 In this book we’re leaving Earth to travel past the Sun across our galaxy and finally out into the universe looking at the countless different types of stars and other objects that fill the cosmos Twinkle Twinkle This book will take you on a journey around the cosmos first to the Sun our nearest star and then through a whole range of objects that reveal the life story of a typical star Finally we’ll take a look at our star-city or galaxy and venture many light years 1 light year is about 5 9 trillion miles or 9 5 trillion kilometers into the cosmos to look at the different types of galaxies that are out there Stars are dense balls of gas that shine because of nuclear reactions in their central cores While most objects in space including planets such as Earth and satellites such as the Moon shine only by reflecting light or sometimes by absorbing and re-emitting it stars create their own energy and light Stars come in a huge range of sizes Some are barely the size of the solar system’s largest planet Jupiter while others are so big they would engulf Jupiter’s entire orbit around the Sun Their brightness also varies greatly from brilliant giants 100,000 times brighter than the Sun to weak dwarf stars see page 19 100,000 times fainter A star’s color is determined by its surface temperature running through the whole rainbow from cool red and orange to scorching blue and violet BEYOND THE SUN WHAT IS A STAR