Week 1 and 2 - Astronomy
Week 1 and 2 - Astronomy ASTR 1307
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This 5 page Class Notes was uploaded by Perla Notetaker on Friday September 4, 2015. The Class Notes belongs to ASTR 1307 at University of Texas at El Paso taught by Noriega-Mendoza, Hector in Fall 2015. Since its upload, it has received 301 views. For similar materials see Elem Astronomy-Solar System in Physical Education at University of Texas at El Paso.
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Date Created: 09/04/15
Aug 28 15 Astronomy The science that studies the material universe beyond the earth39s atmosphere The local celestial sphere is an imaginary dome that surrounds us Is the line resulting from the intersection of this dome with the ground it s the skyline It marks the boundary bW Visible and non Visible sky Is the highest point in the sky located directly overhead Et il E5 W 50 f 5 f franc a x a i x K PE r x e I in 7 f m Iquot E f Observer Chm g Classi cation of stars name eh ELIquot aete r name eh a r aeter name eh a r aete r alpha asquot leta t 139 he p heta leappa a elgma er gamma a lamhda tau 139quot delta 5 mn a upellen 39U epellen E nu 19 phl 35 aeta c all ehl X eta a e mleren a pal theta pl a e mega a Cosmic address We live in an expanding universe Discovery by Hubble and Humason in the 1920 s The universe is about 137 billion years old The Big Bang created the universe There are 88 constellations in the sky 0 Planet earth 0 Solar system 0 Milky Way galaxy 0 Local group of galaxies 0 Virgo Supercluster of galaxies 0 The Universe Local celestial coordinates Too accurately locate an astro we use two local coordinates angles called altitude and azimuth Vertical angle measured from the horizon to the astro Ranges from O to 90 degrees Horizontal angle measured Clockwise along the horizon from the North to the astro Ranges from O to 360 degrees Sept 2 Magnitude system The brightness of stars are specified with the magnitude system The Greek astronomer Hipparchus devised this system around 150 BCE He put the brightest stars into the first magnitude class the next brightest stars into second magnitude class and so on until he had all of the Visible stars grouped into siX magnitude classes The dimmest stars were of sixth magnitude The magnitude system was based on how bright a star appeared to the naked eye 0 The human eye can only see Astros brighter than the 6th mag those whose magnitude is less than 6 0 6 magnitudes classify all stars at night 0 Today we apply it to everything in the sky The smaller the magnitude the brighter the object EX m5 and m3 Magnitude 3 is mgm because 3 is less than 5 EX m 4 and m 7 Magnitude 7 is brighter because 7 is less than 4 m How bright the object appears from Earth M How bright the object actually is Comparing the absolute magnitude of stars 0 M sun 48 dimmest star 0 M sirius 14 0 M betelgeuse 56 brightest star Distance to a star The recipe to estimate the distance to a star is a simple comparison of the apparent and absolute magnitudes such that if 0 m M then the distance 10 pc 0 m lt M then the distance lt 10 pc 0 m gtM then the distance gt 10 pc 10pc 10 X 336 light years 1 parcet pc 336 light years Sept 4 Planet Earth Shape lSt ideas The Visible local horizon looks at to everyone so Earth must be at Pythagoras analogy 6th century BC Earth must be round since the Moon sun and other sources in the sky look round Aristotle s argument Earth is round because its shadow casts on the Moon during lunar eclipse Size Eratosthenes determination of Earth s size Earth s Circumference equals 40000 km Diameter equals about 12000 km Earth s Motion Rotation Earth rotates spins about its axis once every 24 hours Earth s rotational speed Changes with latitude It spins faster at the equator than at the poles Foucault s pendulum The pendulum swings in the same plane as the Earth rotates beneath it It proves that out planet actually spins