AST1002 Exam 1 Study Guide

# AST1002 Exam 1 Study Guide - Light-year = the distance...

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Light-year = the distance light travels in 1 year Distance = velocity X time Speed of Light = 3 X 10 5 km/s (velocity) Seconds in 1 Year = 3.15 10 7 s/year 1 LIGHTYEAR = 9.5 X 10 12 km/year Chapter E: Introduction Astronomy is the study of the Universe. The Universe is finite and very large. It includes everything we observe. Size of solar system is about 40 AU. Solar system has 8 planets, many moons and other materials such as comets, meteorites, etc. The size of our galaxy Milky Way is about 100,000 ly with a very large black hole in the center. Our galaxy has about 10 11 stars and is average in size. We can only see about 6,000 stars with the naked eye. Two units of distance used in astronomy: Astronomical Unit (AU) = 1.5 × 10 11 m is the distance between the Sun and Earth. Light year (ly) = about 1 × 10 16 m is the distance light travels in on year! Observation of an object one million light years away, means we are observing when the light left the object a million years ago, i.e. looking back in time. The sky is divided into 88 constellations. We only see the constellations that are in our night sky. The names of the brightest stars are historical and no new names are given now. The patterns of stars we see are in two dimensions, and the stars are not necessarily close to each other. The stars in a constellation are labeled with Greek letters with the brightest star being α , the second brightest being β , etc. Know how to use the scientific notation, in terms of power of ten. Coordinate system and vocabulary Constellation – a group of stars in a particular location in the sky. A rough coordinate system in the sky. Celestial sphere – imaginary fixed sphere in the sky where all the celestial objects are located. Equator, north and south poles . Altitude – angle above horizon. Azimuth – horizontal angle: north = 0 ° . East = 90 ° . South = 180 ° ° . Zenith – straight up or 90 ° altitude.

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Latitude – on Earth angle above equator. Longitude – on Earth azimuth angle at equator. Declination – equivalent to latitude on the celestial sphere. Right ascension – equivalent of longitude on the celestial sphere. Precession – the 26,000-year motion (wobble) of the North celestial pole. Rotation : rotation on its axis. Earth rotation period is 23 hours 56 min. Revolution : motion around an object. Ecliptic : annual path of Sun amongst the stars. Equator : projection of the equator into the stars (celestial sphere). Vernal equinox : on March 21 when the Sun is on the equator. Summer solstice : when Sun is at highest northern hemisphere elevation on about June 22. Autumnal equinox
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AST1002 Exam 1 Study Guide - Light-year = the distance...

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