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Astronomy.docx - Astronomy Chapter One Star A large,...

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AstronomyChapter OneStarA large, glowing ball of gas that generates hear and light through nuclearfusionThe SunA star like those we see at night. It is the closest star to us.NebulaAn interstellar cloud of gas and/or dustStar ClustersOpen cluster: A few thousand loosely packed starsGlobular cluster: Up to a million or more stars in a dense ball bound togetherby gravityAll of the above terms are elements that make up agalaxy.GalaxyA great island of stars in space, all help together by gravity, gas, dust and soon. Galaxies are not random, rather, there is a structure within all of it whichaids scientists in understanding the galaxy or galaxies. A galaxy is just aportion of theuniverse.UniverseThe sum total of all matter and energy; that is, everything within andbetween all galaxies. All that is visible and invisible.Given the following astronomical objects, the following is the order fromlargestto smallest.Galaxy cluster, Andromeda Galaxy, Nebula, Globular Cluster, The SolarSystem, The Sun, Neutron StarIn the past, scientists believed that the universe was composed of exclusively stars.They believed that looking further and further in space would only show more andmore stars.Our place in the universeEarth is a planet in the Solar SystemSolar System:oSun
oPlanets, Moons, Asteroids, CometsMilky WaySolar System located on Milky Way Galaxy, away from its centerGalaxies are the building blocks of the UniverseGalaxyIsland of stars in spaceoHundred million to several trillion starsMilky Way contains about 100 billion starsBillions of GalaxiesGroups of Galaxies (Local Group)Galaxy Clusters (Virgo Cluster)Superclusters (Local Supercluster)Large Scale structure: The UniverseOur Cosmic Address, HierarchyAstronomical DistancesKilometers (km), Miles (mi): Earth, MoonoCircumference of Earth: about 40,000 km or 25,000 mioAverage Earth-Moon Distance: 239,000 miAstronomical Unit (AU): Solar SystemoEarth-Sun average distance: 1 AU, about 150 million kmoNeptune-Sun distance: 30 AULight Year (ly): Stars, GalaxiesoDistance light travels in one yearAbout 10 trillion km or 63,000 AUDistance to nearest star: about 4.2 lyDistance to Andromeda Galaxy: about 2.5 million lyDiameter of Andromeda Galaxy: 10,000 lyoOne mile is to a light year what a dollar is to the national debt(roughly)oParsec (pa): 3.26 lyComparing Astronomical Distances: Logarithmic ScalesLogarithmic ScaleoEach increment corresponds to a multiplicative factor: 1, 10, 100,1000, …o“Zooming in/out”oUseful to describe quantities that vary by several orders of magnitudeIncome, Net worthAstronomical Distances
Luminosity of StarsLooking backing in TimeoLight from distant stars and galaxies takes longer to reach usWhat we seeThe Sun as it was 8 minutes agoThe Andromeda Galaxy as it was 2.5 million years agooThis proves that 2.5 million years ago, there was auniverseoThe further away we look in Distance the further back we look inTimeo

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Term
Spring
Professor
JackHughes
Tags
Comparing Astronomical Distances

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