ISP Chapter 1 Notes - ISP 205 Chapter 1 Page 1 Basic...

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Chapter 1 Page 1 Basic Astronomical Objects Star – a large, glowing ball of gas that generates heat and light through nuclear fusion in its core. Sun = Star Planet – A moderately large object that orbits a star and shines primarily by reflecting light from its star. Can be considered a planet only if: (1) orbits a star (2) is large enough for its own gravity to make it round (3) has cleared most other objects from its orbital path. An object that has met the first two criteria but not the third, as Pluto, is designated a dwarf planet. Moon (or satellite) – An object that orbits a planet The term satellite is also used more generally to refer to any object orbiting another object. Asteroid – A relatively small any rocky object that orbits a star. Category – “Small solar system bodies” Comet – A relatively small and ice rich object that orbits a star. Category – “Small solar system bodies” Collections of Astronomical Objects Solar System – The Sun and all the material that orbits it (planets, dwarf planets, and small solar system bodies). Specifically refers to our star system (solar = sun), but can apply to other star systems Star System – A star (sometimes more than 1) and any planets and other materials that orbit it. Roughly half of all star systems contain 2 or more stars Galaxy – A great island of stars in space, containing from a few hundred million to a trillion or more stars - Held together by gravity - Orbit a common center Cluster (or group) of Galaxies - A collection of galaxies bound together by gravity. - Groups – Small collections (few dozen galaxies) - Clusters – Larger collections Supercluster – A gigantic region of space where many individual galaxies and many groups and clusters of galaxies are packed more closely together than elsewhere in the universe. Universe (Cosmos) – The sum total of all matter and energy - all galaxies and everything between them Observable Universe – The portion of the entire universe that can be seen from Earth. Probably only a tiny portion of the universe is observable. Astronomical Distance Units
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This note was uploaded on 03/19/2008 for the course ISP 205 taught by Professor Donahue during the Spring '08 term at Michigan State University.

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ISP Chapter 1 Notes - ISP 205 Chapter 1 Page 1 Basic...

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