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Question of the Day Question: What topics do you need to review the most before Friday’s test? Answer: … … … p. 551, # 2 - 7 2. Which of the following is a possible age of the universe, according to the big bang theory? a. 4.6 million years c. 4.6 billion years b. 15 million years d. 15 billion years 3. A pattern of stars as seen from Earth is called a ___________. a. galaxy c. Milky Way b. nebula d. constellation 4. By studying starlight, astronomers may learn which of the following things about stars? a. the elements that compose the star b. the surface temperature of the star c. the speed of the star relative to Earth d. all of the above p. 551, # 2 - 7 5. The core of a star that remains after a supernova may be any of the following except ___________. a. a black hole c. a red giant b. a neutron star d. a pulsar 6. The shape of the orbit of the Earth is _____________. a. a circle c. an arc b. an ellipse d. a sphere 7. The only outer planet that is not a gas giant is ____________. a. Jupiter c. Neptune b. Saturn d. Pluto Galaxy Classification Hubbles systems divides galaxies into three basic catagories Elliptical Galaxies Spiral Galaxies Irregular Galaxies (basically galaxies that don’t look elliptical or spiral) Milky Way Galaxy Our Galaxy Large Spiral Galaxy 100,000 light years across 1000 light years thick Artist’s Conception The Milky Way from Earth Modifications to Hubble’s System Hubble’s system only based on appearance Now we know there are other differences Elliptical Galaxies: mostly old stars, very little gas and dust Spiral Galaxies: mixture of young and old stars, lots of gas & dust so new stars forming Irregular Galaxies: mostly young stars