ASTR 151 Week 1 Notes
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This 3 page Class Notes was uploaded by Wesley Fowler on Saturday January 23, 2016. The Class Notes belongs to ASTR 151 001 at a university taught by Dr. Sean Lindsay in Spring 2016. Since its upload, it has received 41 views.
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Date Created: 01/23/16
Wesley Fowler ASTR 151 152 Reading 1.1-1.3 Scientific Method Scientific method: The process of testing a theory via a controlled and measured experiment Theory: “The framework of ideas and assumptions used to explain some set of observations and make predictions about the real world”(8 McMiillan). Theoretical model: Result of theory, a representation. Qualifications for a theory: -Testable -Continually tested -As “simple” as possible -elegant Mapping the Universe Planet-star-system-galaxy-cluster-universe Universe: The totality of space Astronomy: The study of the universe 1 Light year= 10 trillion kilometers or 6 trillion miles -speed of light= 300,000 kilometers per sec Fixed background: The stars appear to hold relative fixed positions in the sky Constellations: Ancient observations of how stars connect into configurations. Used to pinpoint the location of stars. Smaller groupings of stars with casual names are called asterism. For example the “Big Dipper”. Celestial sphere: The simple concept that earth resides in a celestial sphere in which stars travel in a fixed relative location. Earth’s poles coincide with the universe’s poles. Divided into 88 constellations. - Right Ascension: Equates to longitude for celestial sphere, horizontal - Declination: Equates to latitude celestial sphere, vertical - The grid of locating stars and objects on the celestial sphere http://www.daviddarling.info/encyclopedia/C/celsphere.html The zodiac is comprised of the constellations that are aligned on the ecliptic. The ones that the sun passes through. Eath’s Motions Diurnal: Daily - Rise in the east, set in the west Annual: Yearly - Due to earth’s revolution, or orbital motion Sidereal: Rotation or revolution of 360 degrees. Rotation: Earth is tilted at 23.5 degrees with respect to its orbital path. In summer, the Sun rises north of east, travels through the southern sky, and sets north of west. In winter, the Sun rises South of East, travels through southern sky, and sets south of west Solar Day: Noon-to-noon (24 hours) Sidereal Day: Time for 360-degree rotation (23 hours 56 minutes) Revolution: 0.986 degrees per day Seasons are determined by the Earth’s 23.5 axial tilt! The planet is closest to the sun during January, but due to the concentration of sunlight, it’s the coldest season in the north and the warmest in the south. Wesley Fowler ASTR 151 152 Intro to Astronomy Astro-Star Nomy-Law Oldest of the sciences 5 1 Kilometer = 1,000m = 10 cm 1 astronomical unit (AU) = 1.496 x 10 m (avg distance between the earth and the sun) 15 12 1 light year (ly) = 9.46 x 10 m = 9.45 x 10 km = 63,200 AU (distance light travels in a year) 1 Parsec (pc) = 3.09 x 10 m = 206,000 AU = 3.26ly “One parsec corresponds to the distance at which the mean radius of the earth's orbit subtends an angle of one second of arc” 3.0 x 10 m/s = speed of light Giga: Billion Mega: Million Kil: Thousand Centi: .01 Micro: 10^-6 Nano: 10^-9 Earth= 12,800 km 10 Solar System= 10 km Milky Way= 10 km= 100,000 ly Virgo closest to milkyway, millions of light years? Everything is being drawn towards “The great attractor” which is made of dark matter and galaxies 100 Billion stars in milky way galaxy 100,000 light years across the galaxy 7 Seconds in a year = x 10 sec Scientific theory: Observation-theory-predictions/hypothesis-observation… Data-hypothesis-test-results
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