Midterm #1 Study Guide!!! This is a must download, very DETAILED!

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Astronomy & Astrophysics
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Clifford Orwin

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AST101 The Sun and Its Neighbours Midterm #1 Study Notes Chapter 1 5 Chapter 1 Our Place in the Universe GEOCENTRIC earth-centered universe SOLAR SYSTEM (star system) consists of a star (sometimes more than one star) and all the objects that orbit it [consists of the Sun and all the objects that orbit it: the planets and their moons, asteroids (chunks of rocks), comets, and countless tiny particles of interplanetary dust] MILKY WAY Used both as the name of our galaxy and to refer to the band of light we see in the sky when we look into the plane of the Milky Way Galaxy GALAXY a huge collection of anywhere from a few hundred million to more than a trillion stars, all bound together by gravity LOCAL GROUP the group of more than 30 galaxies to which the Milky Way Galaxy belongs GALAXY CLUSTERS (cluster of Galaxies) a collection of a few dozen or more galaxies bound together by gravity; smaller collections of galaxies are simply called groups (groups of galaxies with more than a few dozen members) SUPERCLUSTERS consists of many clusters of galaxies, groups of galaxies, and individual galaxies and are the largest known structures in the universe LOCAL SUPERCLUSTER the Supercluster of galaxies to which the Local Group Belongs UNIVERSE the sum total of all energy and matter BIG BANG The event that gave birth to the universe LIGHTYEARS the distance that light can travel in 1-year, about 9.46 trillion km6 trillion miles ONE LIGHTYEAR OBSERVABLE UNIVERSE the portion of the entire universe that we can potentially observe (consists only of objects that lie within 14 billion light-years) ASTRONOMICAL UNIT (au) equivalent to about 150 million km ECLIPTIC PLANE the plane of the Earths orbit around the Sun AXIS TILT 23.5 degrees in relation to ecliptic plane Chapter 2 Discovering the Universe for Yourself CONSTELLATION a region in the sky; 88 official constellations cover the celestial sphere CELESTIAL SPHERE the imaginary sphere on which objects in the sky appear to reside when observed from Earth shows us how stars appear to be arranged in the sky (constellations) North Celestial Pole the point directly over Earths North Pole South Celestial Pole The point directly over Earths South Pole Celestial Equator a projection of Earths equator into space, makes a complete circle around the celestial sphere www.notesolution.com Ecliptic the path the Sun follows as it appears to circle around the celestial sphere once each year ECLIPTIC PLANE the plane of the Earths orbit around the Sun LOCAL SKY the sky as seen from wherever you happen to be standing HORIZON the boundary between the Earth and the sky ZENITH the point directly overhead (has an altitude of 90degrees BUT NO DIRECTION because it is straight overhead) MERIDAN an imaginary half circle stretching from the horizon due south, through the zenith, to the horizon due north AZIMUTH (DIRECTION) direction along the horizon (used to pinpoint the position of any object in the local sky) N E S W ALTITUDE (above the horizon) ANGLUAL distance between the horizon and the object in the sky ANGULAR SIZEDISTANCE a measure of the angle formed by extending imaginary lines outward from our eyes to span an object (or between two objects) - SIZE angle of an object that it appears to span in your field of view - DISTANCE the angle that appears to separate a pair of objects CIRCUMPOLAR stars that always remain above the horizon for a particular latitude CHAPTER 4 Making Sense of the Universe SPEED the rate at which an object moves. Its units are distance divided by time, such as ms or 100 kmhr (s=dt) VELOCITY the combination of speed and direction of motion; it can be stated as speed in a particular direction, such as 100kmhr due north ACCELERATION the rate at which an objects velocity changes. Its standard units are ms (change in velocity speeddirectionboth) ACCELERATION OF GRAVITY the acceleration of a falling object (abbreviated g=9.8ms) MOMENTUM the product of an objects mass and velocity (MO=MASS*VELOCITY) FORCE anything that can cause a change in momentum (ONLY way to change momentum) NET FORCE overall force to which an object responds; the net force is equal to the rate of change in the objects momentum (NF = MASS*ACCELEATION) ANGULAR MOMENTUM momentum attributable to rotation of revolution (circular movements); the angular momentum of an object moving in a circle of radius r is the product m*V*r ROTATIONAL ANGULAR MOMENTUM ORBITAL ANGULAR MOMENTUM TORQUE a twisting force that can cause a change in an objects angular momentum MASS amount of matter in your body WEIGHT the net force that an object applied to its surroundings (humans on Earth weight = mass*acceleration of gravity) FREE FALL falling without any resistance to slow you down WEIGHTLESS a weight of zero, occurs during free-fall www.notesolution.com
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