The Sun, Stars, and Galaxies

The Sun, Stars, and Galaxies — page 1 — MN winkle twinkle little star How I wonder what you are Readers of this book will wonder no more In these pages lies information on the prop erties and characteristics of stars including one star that is vital to life on Earth the Sun Topics include star composition brightness and configuration into constellations the layers of the Sun and its role as the center of the solar system and the shape of and energy emitted by large groups of stars known as galaxies The scientific exploration of these illuminated celestial bodies through the years is also covered Up above the world so high Like a diamond in the sky The common image of stars as tiny points of light softly twinkling in the night sky belies their truly awesome power Even their births are intense Stars are formed when gravity forces a cloud of dust and debris to contract causing a violent collision of hydrogen atoms This high level of intensity carries through the life of a star as its core or nucleus burns courtesy of continuous explosions that are

The Sun, Stars, and Galaxies — page 2 — INTRODutrios like nuclear bombs detonating Eventually all the fuel in the core gets used up and many stars simply collapse in upon themselves This process leaves a small core that will eventually burn itself out as it cools Some stars however go out in spectacular fashion as supernovas exploding into vast fields of debris that even tually contribute to the creation of new stars In the vast scheme of the universe the Sun is a pretty average star It is estimated to be nearly 5 billion years old which means it still has billions of years to shine before it reaches the end of its life cycle Size wise the Sun falls somewhere in the middle between massive giants and tiny dwarfs Within the solar system however the Sun is anything but average Here it is the center of all the action A full 99 percent of the solar system s mass is taken up by the Sun Eight planets and their satellites the dwarf planets and an assortment of meteors asteroids and other celestial bodies account for the remaining 1 percent Although it is roughly the same size as billions of other stars the Sun appears larger because it is relatively close 93 million miles 150 million kilometers to Earth At the center of the Sun is the core an extremely dense pressure filled collection

The Sun, Stars, and Galaxies — page 3 — THE SUN STARS AND GALAXIES Stephan s yintet a group of galaxies with stars of many ages and A colors as seen from the Hubble Space Telescope NASA ESA and the Hubble SM4 ERO Team

The Sun, Stars, and Galaxies — page 4 — INTRODUCTION of atomic particles Heat and light are emit ted from the photosphere which is the Sun's surface layer The photosphere is in constant motion due to rolling solar waves Another characteristic of the photosphere is sun spots which are cooler dark patches caused by strong magnetic activity Higher levels of the Sun's atmosphere are the chromosphere and the corona which are not as visible as the photosphere but are actually much hotter Planets orbit the Sun but the Sun has an orbit of its own around the center of the Milky Way galaxy The Milky Way is just one of many of these enormous collections of stars that make up the universe Agalaxy con sists of millions or even hundreds of billions of stars in any of a variety of shapes ellipti cal spiral barred spiral or irregular which seem kind of formless The Milky Way is a spiral galaxy Twinkle twinkle little star Now I know just what you are

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