<p>Name:______Date:______Pd:______Historical Models of Solar System Heliocentric Theory Geocentric Theory (“GEO” (“HELIO” CENTRIC) CENTRIC) Meaning of the Prefix</p><p>Definition</p><p>Astronomer Who Proposed the Theory DIAGRAM</p><p>1. ______is the study of the universe. A scientist who studies the universe is called an ______.</p><p>2. ______is the distance that light travels in one year; about 9.46 trillion kilometers. This unit is used to measure distance of objects in space. Galaxies (pages 596-597)</p><p>Galaxies (Types of Galaxies)</p><p>A large group of stars, dust and gas are called______. There are many different types of galaxies. ______, the astronomer for who the ______is named, began to classify______, mostly by their shapes, in the 1920’s.</p><p>Spiral Galaxies </p><p>______galaxies have a bulge at the center and spiral arms. The spiral arms are made up of ______, ______, and ______that have formed in these denser regions of gas and dust. </p><p>The Milky Way</p><p>Observing other galaxies and making measurements inside our galaxy, the ______, has led astronomers to think that our solar system is in a ______galaxy.</p><p> We live in the ______galaxy.</p><p> What is the shape of the Milky Way Galaxy? ______</p><p>Formation of the Universe (pages 600-601)</p><p>Big Bang Theory (What is it? When was it developed? Where did the evidence come from to support the Big Bang?)</p><p>______</p><p>Place the following in order from the Largest to the Smallest: Earth, Sun, Moon, Milky Way Galaxy, Universe, Solar System.</p><p>Largest Smallest </p><p>1. 2. 3. 4. 5. 6.</p>