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20.2 The Milky Way and Other Galaxies
I can: -explain that gravity is the force that binds together dust and gas to form stars, star systems, and star clusters -recognize that there are billions of galaxies in the Universe and they can be classified by size and shape. -classify the Milky Way as a spiral galaxies. -describe the Milky Way galaxy as having more than 100 billion stars and a diameter of more than 100 thousand light years -recognize that at the center of the Milky Way there is a bulge stars, from which are spiral arms of gas, dust and most of the young stars. -recognize that the solar system is part of the Milky Way galaxy. K -demonstrate that Hubble’s law that galaxies that are farther away have a greater red shift, so the speed at which a galaxy is moving away is proportional to its distance from the Earth. S -explain that the phenomenon due to Doppler shifting, so the shift of light from a galaxy to the red end of the spectrum indicates that the galaxy and the observer are moving farther away from one another
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Galaxies Collection of stars, dust, and gas bound together by gravity.
Held together by gravity Cluster: a group of stars or galaxies bound together by gravity Milky Way and Andromeda belong to LOCAL CLUSTER. Superclusters Can be 100 million light years across.
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Types of Galaxies
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The Milky Way is a spiral galaxy
Interstellar matter: the gas and dust located between the stars in a galaxy.
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