E-Book Overview
When a puddle dries up, where does all the water go? The science matters series provides a compelling introduction to key science topics, explaining concepts in a format that encourages reading and comprehension. Each title introduces a core science topic through visual diagrams, hands-on experiments, and fascinating biographies, all engagingly written.
E-Book Content
Studying Stars The night sky is dotted with tiny, twinkling stars. They look like specks of light in the distance. All stars appear small from Earth because they are so far away. In fact, stars are very large. Did you know that the Sun is also a star? Some stars are larger than the Sun. Others are smaller than the Sun. The mass of some stars can be about 10 times greater than the Sun.
. People can see stars in the sky because of the light energy the stars produce.
Star Facts Did you know that the Sun produces enough energy o power the United States? One second of the Sun' inergy could provide power to the United States for [ million years. I
• Stars burn for billions of years.
• The Sun is a star. It is the closest star to Earth.
• After the Sun, the next nearest star to Earth is called Próxima Centauri.
• The smallest white dwarf stars are the same size as Earth.
• Ocean sailors once used stars to guide their way.
• A star's brightness is called luminosity.
Earth's Closest Star Earth is about 93 million miles (150 million km) from the Sun. The Sun is the only star whose heat reaches our planet. Sunlight takes slightly more than 8 minutes to reach Earth. Light from the other stars takes much longer to reach Earth. This is because all of the other stars are much farther away.
Earth receives the heat of the Sun. Without the Sun's heat Earth would be cold, dark, and lifeless.
ery large stars are called supergiants. Supergiants ventually die out. When they die, they explode in fiery blaze. This explosion is called a supernova.
Supernovas can be bright enough to see from Earth. In the year 1054, people from all over the world saw a bright light in the sky.The light shone for 23 days. The supernova could be seen during the day.
Starry Nights Stars are huge, glowing balls of swirling gases. One of these gases is called hydrogen. Stars are so hot that the hydrogen gas breaks apart. The heat causes hydrogen to change into helium. The change produces a large amount of energy. Some of the energy takes the form of heat. Some of the energy takes the form of light.
• Scientists measure the size of stars by studying their brightness and temperature.
Star Colors Stars are one of three different colors. Some stars are yellow. For instance, the Sun is a yellow star. Other types of stars are blue or red.
A star's heat affects the color that can be seen fronn Earth. Imagine a burning candle. The blue part of the flame is the hottest part.The yellow part is less hot.The red part of the flame is the coolest. Which type of stars do you think are hottest: red or blue?
Star Patterns More than one thousand stars can be seen on a very dark night. People in ancient times saw patterns when they looked up at the twinkling stars. They imagined lines that connected the stars. These lines formed shapes. Some star shapes looked like animals, such as bears or dogs. Other star shapes formed gods or goddesses. Star patterns are called constellations.
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"- Ursa Major (bottom) is called the Great Bear. Ursa Minor (top) is called the Lesser Bear.
Star Shapes Md you know that the northern half of Earth sees a ifferent part of the sky than the southern half? Thi leans that the two halves of the world see differen onstellations in the night sky.
Constellations were created long ago. People in different parts of the world s