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Earth and The Solar System. Earth Science 2013 Pulford. The Universe. Astronomers define the universe as all of space and everything in it . Galaxies. A galaxy is a huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity.
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Earth and The Solar System Earth Science 2013 Pulford
The Universe • Astronomers define the universe as all of space and everything in it.
Galaxies • A galaxy is a huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity. • There are billions of galaxies in the universe. • The largest galaxies have more than a trillion stars.
Galaxies • Astronomers classify most galaxies into the following types: • Spiral • Elliptical • Irregular
Our GalaxyThe Milky Way • Our solar system is located in a spiral galaxy called the Milky Way. • From the side, the Milky Way would look like a narrow disk with a large bulge in the middle. • But from the top view, the Milky Way would have a spiral, pinwheel shape.
Milky Way-Side View Sun’s location
Milky Way-Top View Sun s location
The BIG BANG • Accepted theory about how the universe was created • About 13.7 billion years ago, the universe was no larger than the period at the end of this sentence. • This tiny universe was incredibly hot and dense. • The universe then exploded in what astronomers call the big bang.
Scientific Proof behind the Big Bang Theory • Edwin Hubble was able to study other galaxies and see if the were moving towards us or away from us • He could also tell us how fast they were moving (most galaxies are moving away from us) • Hubble’s law states that the farther away a galaxy is, the faster it is moving away from us. Hubble’s law strongly supports the big bang theory.
Scientific Proof behind the Big Bang Theory • Cosmic Background Radiation • In 1965, two American physicists accidentally detected faint radiation on their telescope. • This mysterious glow was coming from all directions in space. • Scientists later concluded that this glow is the leftover heat energy from the big bang. • This energy was distributed in every direction as the universe expanded.
Graphic Organizer Evidence THEORY