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Date: Entry: Galaxies and the Universe Pg. 394 - 399 1. The Universe • A. space and everything in it • B. Contains billions of galaxies and lots and lots and lots of empty space How Big is it? (don’t copy until I tell you to start) It would take 2 million years to reach the next closest galaxy. • If our galaxy were the size of a dime, the Andromeda Galaxy, our closest neighbor, would be about half a meter away. The rest of the universe, as far as astronomers can see, would extend for about 2 kilometers (1.2 miles) in all directions. • If a space ship could explore the area around one star every minute it would still take nearly a million years the explore every star in our galaxy. start copying here 2. Origin of the Universe, 3 theories • A. steady state theory. • I. the universe always has been and always will be the same as it is now. • B. the oscillating model. • I. began by expanding. • II. the expansion slowed and the universe contracted. • II. Then process began again, oscillating back and forth. (Like an oscillating fan) • C. most excepted big bang theory. • I. The universe started with a big bang and has been expanding ever since. • II. Exploded about 13.7 billion years ago. • III. The entire universe began to expand at the same time. • IV. Supported by the fact that most things in the universe are moving away from a central point • V. Whether the universe will expand forever or stop expanding is still unknown. http://www.learn360.com/ShowVid eo.aspx?lid=26813047&SearchTex t=Big+Bang+Theory&ID=754560 3. Galaxies • A. Giant structures containing I. billions of stars, planets, lots of gas, and dust, held together by gravity. • B. our solar system is in the Milky Way Galaxy • C. separated by millions of lightyears. • I. A light-year is the distance light travels in one year. • II. About 9.5 trillion km (5.8 trillion miles) at the speed of 300,000 km per second III. Traveling at the speed of light, it takes 4.2 years for light from the next closest star system to reach Earth a. about 40 trillion km away IV. Light from our sun takes 8 min. • 4. The three major types of galaxies A. Spiral Galaxies • I. have spiral arms that wind outward from the center. • II. consist of bright stars, planets, moons, dust, and gas. III. 2/3 of spiral galaxies are Barred spiral galaxies Spiral Galaxies B. Elliptical Galaxies • I. Looks like a flattened football • II. Most common type • III. Contains only old stars and very little dust and gas. C. Irregular Galaxies • I. Includes galaxies that don't fit into the other categories • II. have many different shapes. • III. They are smaller than the other types of galaxies. 5. The Milky Way Galaxy • A. spiral galaxy • B. contains about one trillion stars. • C. 100,000 light-years across. • D. Our Sun is located about 26,000 light-years from the center • E. All stars orbit around a central region, or core. • F. Takes 225 million years for our solar system to orbit the center • G. may have a massive black hole at its center. • H. black hole more than 2.5 million times more massive then the Sun. Milky Way from La Silla Taken from a farm in Iowa Interesting fact: • Ancient Greeks saw a milky belt in the southern night sky and they attributed its origin to Hera the goddess. While nursing Heraklis she spilled some of her milk in the sky - and that milk created the Milky Road to Heaven! This is how they called our Galaxy! • http://www.learn360.com/ShowVideo.aspx ?lid=26813047&SearchText=milky+way+g alaxy&ID=132632 Galaxies Review Sheet Type Spiral Elliptical Irregular Picture Information