Understanding Our Sun

Understanding Our Sun book cover — Contents CHAPTER 1 Our Amazing Sun CHAPTER 2 Looking at the Sun CHAPTER 3 Inside the Sun CHAPTER 4 Solar Power CHAPTER 5 Solar Danger CHAPTER 6 What’s Next ACTIVITY Your Space Science Mission Glossary Learning More Index and About the Author 4 10 20 26 34 40 44 46 47 48

Understanding Our Sun — page 1 — CHAPTER 1 Our Amazing Sun Our Solar System is our home in the universe As well as Earth it comprises seven other planets dozens of dwarf planets and moons and millions of asteroids and comets flying around At the center of everything is the Sun It makes up 99 8 percent of all the mass of our Solar System Its gravity keeps Earth and the other objects in predictable orbits which are regular paths around the Sun The surface of the Sun is around 9,932 Fahrenheit 5,500 C and its energy gives us light and heat At the Center Our Sun is a star like one of about 250 billion others in the galaxy Each star is surrounded by its own solar system of planets and other objects Along with the Moon the Sun is one of the easiest celestial objects or objects in the sky to see from Earth It is only in the past couple of centuries however that people have looked at the Sun in a scientific way They ask questions about the Sun’s physical qualities How was it created Why is it so hot Has it changed Will it continue to change Earth’s atmosphere is an envelope of gases that surround the planet The atmosphere distorts the Sun’s light making it look as though it has rays 4

Understanding Our Sun — page 2 — MISSION Space Science Our Sun is 1 astronomical unit AU from Earth An AU is a unit of length used by astronomers to measure distances in space It is defined as the average distance between Earth and the Sun This is about 93 million miles 149,668,992 km At its widest the diameter of the Sun is about 865,000 miles 1 4 million km The volume of the Sun is huge it is so large that 1 3 million Earths could fit inside it Scientists darken bright images of the Sun to reveal details of the activity on its surface It is impossible to send spacecraft to the Sun It is too hot for anything to approach without being destroyed But by studying the Sun with different scientific instruments people have come to know a lot about it We know what it is made of We know that it is 4 603 billion years old which is more than 60 million years older than Earth Many questions still remain however Scientists are just beginning to unravel the secrets of the Sun New Discoveries Careful observation and advanced technology reveal new information about the Sun Astronomers are scientists who study space Using the Hinode spacecraft they found that the Sun’s surface bristles with jets of X-rays These jets fire blobs of energy off the surface at about 1 9 million miles per hour 3 2 million kph Even after centuries of watching the Sun our star continues to surprise us 5

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