PHY121 Ch 1 Notes

PHY121 Ch 1 Notes - Astronomy Chapter 1: Here and Now You...

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Astronomy Chapter 1: Here and Now You surveyed the universe by taking a cosmic zoom in which each field of view (region you can see in the image) was 100 times wider than the previous field of view. Astronomers use the metric system because it simplifies calculations and use scientific notation for very large of very small numbers. You live on a planet , Earth, which orbits our star , the sun, once a year. As the Earth rotates once a day, you see the sun rise and set. The moon is only one-fourth the diameter of Earth, but the sun is 109 times larger in diameter than Earth – a typical size for a star. The solar system includes the sun at the center and all of the planets that orbit around it – Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. The astronomical unit (AU) is the average distance from Earth to the sun. Mars, for example, orbits 1.5 AU from the sun. The light-year (ly) is the distance light can travel in one year. The nearest star is 4.2 ly from the sun.
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