MISSION EXPLORING SIRIUS On a clear night you can see more than 2 000 twinkling stars You might also see a bright glowing band This band is our home galaxy the Milky Way There are so many stars there they look like a single glowing streak Bright Light Some stars are brighter than others But that doesn't mean they're closer to us Barnard's Star is about 12 trillion miles 19 trillion km from Earth It is very dim Sirius is the brightest star in the night sky But it is more than 51 trillion miles 82 trillion km away More than Meets the Eye From Earth stars seem like tiny specks But they are larger than they appear Our star the sun is 100 times wider than Earth Other stars are much larger
There are about 300 billion stars in the Milky Way galaxy A Long Journey Looking at stars is like looking back in time It takes many years for a star's light to reach Earth What were you doing eight and a half years ago That was when the light you see left Sirius
CHAPTER 1 MEET A STAR Stars are celestial bodies that produce their own light The universe contains more than 100 billion galaxies And each galaxy contains billions of stars That means the universe contains trillions of stars Stars range in size and brightness They are all made up mostly of gases But each star can contain different amounts of elements Our sun is an average star It is medium in size and its core is about 27 000 000 degrees Fahrenheit 15 million°C That sounds extremely hot But it is an average temperature for a star Some stars can burn up to 10 billion degrees Fahrenheit 5 6 billion°C Eight planets orbit our sun Scientists believe many other stars have planets orbiting them too But ours is the only solar system known to contain life
Approximately 1 300 000 Earths could fit inside the sun
