The Sun, Stars, and Galaxies

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

The Sun, Stars, and Galaxies — page 5 — THE SUN THE CENTER OF THE SoLAR SYSTEM lthough the Sun is a rather ordi nary star it is very important to the inhabitants of Earth The Sun is the source of virtually all Earth’s energy 6 approximate size of Earth A huge cloud of gas erupts from the Sun The image is in false color and was taken in extreme ultraviolet light An image of Earth has been superimposed to show how enormous the Sun is in comparison SOHO ESA NASA Io

The Sun, Stars, and Galaxies — page 6 — THE SUN TuE CENTER OF THE SOLAR SrsTEM It provides the heat and light that make life on Earth possible Yet Earth receives only about half a billionth of the energy that leaves the Sun The Sun is a huge ball of hot gases Like other stars it produces enormous amounts of energy by converting hydrogen to helium deep within its interior PosITION IN SPACE The Sun lies at the center of the solar system It contains more than 99 percent of the sys tem's mass The immense pull of its gravity holds the planets dwarf planets asteroids comets and other bodies in orbit around it The average distance between the Sun and Earth is roughly 93 million miles 150 million kilometers Light travels through space at about 186 282 miles 299 792 kilometers per sec ond so a ray of sunlight takes only about 8 minutes to reach Earth Light from other stars takes much longer to reach Earth light from the next nearest star Proxima Centauri takes more than four years to arrive The Sun is in the outer part of the Milky Way galaxy Light from the center of the galaxy takes many thousands of years to reach Earth II

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