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Name: _____________________________________ Date: ________________ Period: ___ SPACE SCIENCE Reading Review The universe is estimated to be over 10 billion years old. The universe is composed of galaxies, stars, planets, asteroids, comets, and meteors, each having different properties. Our solar system exists within the Milky Way galaxy. The known components of our solar system are the Sun, four terrestrial planets (Mercury, Venus, Earth, Mars), four gas giants (Jupiter, Saturn, Uranus, Neptune), Pluto (one of the three dwarf planets), as well as numerous moons, comets, asteroids, and meteors. Each of these celestial objects has its own unique characteristics. 1. How old is the universe? ______________________________________ 2. True or False. Asteroids and comets have the all same physical properties. ___________ 3. List the components of our solar system: Our star, the ____________________, Four terrestrial planets ______________________________________________________, Four gas giants _______________________________________________________, Dwarf planets such as ______________, and other celestial objects such as __________, _________________, ________________________, and _____________________. The universe, all of space and everything in it, contains billions and billions of stars and galaxies. A galaxy is a giant structure that contains hundreds of billions of stars. Galaxies have been classified into three main categories based mainly on shape: spiral, elliptical, and irregular. Spiral galaxies consist of a central nucleus of bright stars and flattened arms of stars that spiral around the nucleus. The spiral arms contain millions of young stars, gas, and dust. Elliptical galaxies vary in shape from nearly spherical to flattened disks. They are different from spiral galaxies in that they do not have spiral arms. This indicates that elliptical galaxies have no young stars and contain very little gas and dust. Finally, irregular galaxies do not have any particular shape. Irregular galaxies have young stars and a lot of gas and dust. Irregular galaxies tend to be smaller and fainter than other types of galaxies and appear to have an uneven distribution of stars throughout the galaxy. 4. What is the definition of the universe? ________________________________________ 5. How many galaxies in the universe? __________________________________________ 6. How many stars are in galaxies? _____________________________________________ 7. Define a galaxy. __________________________________________________________ 8. By which characteristic are galaxies classified? _________________________________ 9. What are the three main categories of galaxies? _________________________________ 10. Fill in the chart with the correct characteristics of each type of galaxy. Draw shape Types of stars A lot or a little Other (young or old) Gas and dust characteristics Spiral Elliptical Irregular 1 Our solar system is a just a small speck within the Milky Way Galaxy. The Milky Way Galaxy is a spiral galaxy. The Milky Way Galaxy has a diameter of about 100,000 light years, with the sun being located about 30,000 light-years from the center of the galaxy. 11. What type of galaxy is the Milky Way? _____________________________ 12. Draw the milky way galaxy. 13. True or False. Our solar system is located in the center of the Milky Way galaxy. _______________ Stars are huge spheres made mostly of gasses and can produce their own light. Light is released as a result of nuclear fusion in the core of stars. Astronomers classify stars according to their size, temperature, and brightness. A star’s temperature is indicated by its color. Cooler stars appear red in the night sky and hotter stars appear blue. Brightness, the amount of light stars give off, varies from star to star. How bright a star looks from Earth depends on both how far the star is from Earth and how bright the star actually is. Apparent magnitude is how bright a star appears from Earth whereas absolute magnitude is how bright a star would appear if it were a standard distance from the earth. A star’s temperature and brightness can be plotted on a graph known as the Hertzsprung- Russell Diagram. 14. What are stars made of? ___________________________________________________ 15. What do stars produce? ________________________ 16. How are three ways stars are classified? _______________________________________ ___________________________________________________________________________ 17. What color are cool stars? _________________________ 18. What color are the hottest stars? _____________________________ 19. True or False. Every star gives off the same amount of brightness. _____________ 20. What characteristics of a star are plotted on the Hertzsprung Russell Diagram? ________________________________________________________________________ 2 A collection of planets, moons, asteroids, comets, and meteoroids orbiting around a central star is known as a solar system. None of these objects except the star can produce its own light. The closest star to Earth is the sun, the center of our solar system. Its mass makes up 99.8% of the total mass in the solar system. Due to its size, the sun’s gravitational pull is strong enough to hold all of the planets and celestial bodies in orbit. Like Earth, the sun has an interior and an atmosphere. The interior of the sun, the core, acts like a giant furnace releasing energy from nuclear fusion. The temperature inside the sun’s core can reach up to 15 million degrees Celsius. The sun’s atmosphere is divided into three layers: the photosphere, chromosphere, and corona. On the photosphere, there are darker areas where the gases are cooler than the surrounding gases. These areas are called sunspots. These sunspots usually occur in pairs or groups. Prominences are reddish loops of gases that connect two sunspots. Occasionally, when these loops connect, there are explosions of gases called solar flares. This can cause fluctuations in our weather and radio communications on Earth. 21. What is a solar system? ___________________________________________________ _________________________________________________________________________ 22. What is the only celestial object that can produce light? _________________________ 23. What is the closest star to Earth? ___________________ 24. What is in the center of the solar system? ___________________________ 25. What holds all the planets, asteroids and comets in orbit around the Sun? ____________ 26. What is the temperature of the sun’s core? _____________________________________ 27. What are the darker spots on the outside of the sun’s photosphere called where gases are cooler? __________________________ 28. What can cause changes in our weather and radio communications on Earth? _______________________________ The four inner planets, Mercury, Venus, Earth and Mars, are more similar to each other than they are to the four outer planets. They are called the terrestrial planets because they are smaller and have rocky surfaces. The word terrestrial comes from the Latin root word terra, which means “Earth.” Unmanned space missions have collected data regarding conditions on Mercury, Venus, and Mars. The probe Mariner10 photographed Mercury in 1974. Most of what we know about Venus comes from data collected by the Megellan probe in 1990. Various missions to Mars, such as Pathfinder in 1997, have collected data utilizing a remote-control rover called Sojourner. Evidence from these space missions indicates that terrestrial planets are similar in that they all show evidence of geologic activity such as volcanoes. 29. List the four inner planets. __________________________________________________ 30. What is another name for the inner planets? ____________________________________ 31. True or False. Unmanned space mission indicate that the terrestrial planets are very similar to each other. ___________________ 3 The four outer planets (Jupiter, Saturn, Uranus, and Neptune) are known as the “gas giants,” because they are much larger than Earth and are made almost entirely of gases. Since the gas planets have so much mass compared to the inner planets, they exert a much stronger gravitational force. Pluto is considered a dwarf planet. Most of what is known about the outer planets has come from observations by the NASA space probes Voyager 1 and Voyager 2. 32. List the four outer planets. __________________________________________________ 33. What is another name for the outer planets? ____________________________________ 34. List three ways the outer planets are different from earth. a. __________________________________________________________________ b. __________________________________________________________________ c. __________________________________________________________________ Orbiting many planets are smaller satellites called moons. A moon is a spherical object that orbits a planet. Just like the terrestrial planets, some moons also show evidence of geologic activity. For example, Earth’s moon has evidence of moonquakes and lava flows. Also, one of Jupiter’s many moons, Io, is the only satellite in our solar system known to have active volcanoes. In addition, it has lava flows, volcanic deposits, and large volcanic craters. 35. What does a moon orbit around? __________________________________ 36. What is another name for a moon? _________________________________ 37. True or false. Some moons have evidence of earthquakes, known as moonquakes, and volcano activity. ___________________ Additional celestial objects within our solar system include comets, asteroids, and meteoroids. Asteroids are objects revolving around the sun that are too small and numerous to be considered planets. Most asteroids can be found orbiting the sun in a region between Mars and Jupiter known as the Asteroid Belt. Smaller pieces of rock and dust found in a solar system which are similar to asteroids are known as meteoroids. When meteoroids enter an atmosphere they burn up which causes a streak of light in the sky. This streak of light is called a meteor. If the meteoroid is too large and does not completely burn up in the atmosphere, it will strike the surface and become a meteorite. Finally, a comet is a ball of ice and dust whose orbit is a long, narrow ellipse. Gas and dust found in the tail of the comet are illuminated by the sun, which causes the comet’s fiery appearance in the night’s sky. 38. Why are asteroids not considered planets? ___________________________________ _________________________________________________________________________ 39. Where are asteroids located in the solar system? ________________________________ 40. Explain or draw the process of a meteoroid becoming a meteor and then a meteorite. 41. What is a comet made of? _________________________ 4