Astronomy AST2002-16Fall 0001
University of Central Florida
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This 4 page Class Notes was uploaded by Becca Petersen on Thursday September 15, 2016. The Class Notes belongs to AST2002-16Fall 0001 at University of Central Florida taught by Dr. James Cooney in Fall 2016. Since its upload, it has received 144 views. For similar materials see Astronomy in Science at University of Central Florida.
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Date Created: 09/15/16
Astronomy Chapters 1 -3 (book/class notes) Picture of the day: Density of “stuff” (gas and dust) is actually very thin Hydrogen and helium – almost all of the universe is hydrogen and the parts that aren’t hydrogen are helium Scattered blue light – is light reflectant and scattered off of the new stars Red light – is omitted light from the gases 10 billion is 10^10 1 million is 10^6 10^11+10^14=10^25 (just know how that works) Earth – solar system – galaxy-‐ local group – super cluster – universe Dimensions and units: Length-‐ SI (shorthand for the metric system) – meter – distance light travels in 1/299792458 s – meter becomes too cumbersome to deal with when distances become too large. So in order to not have to carry around a bunch of powers of tens we us the following . . . Astronomical Unit (AU) – 150 million km – average distance from the earth to the sun – an average because we don’t orbit in a perfect circle around the sun (standard unit of distance for anything within our solar system) Light Year – 9.5 trillion km – the distance that light can travel in a vacuum in one year – it is not time it is a distance – good for measuring our neighborhood as far as stars are concerned Parsec – How far away a star would have to be to appear to shift by one arc second when the earth moves by one AU. 30 trillion km (definition is a little complicated but it is essentially three light years) 2 concepts that go into its definition: Concept 1: Parallax – it is something you experience in your everyday life – it is the apparent motion of something not because it’s actually moving but because the observation point has changed. We can use that to measure the distance to stars. The closer the object is, the more it will shift (when we switch eyes/observation points) Ex: hold out your finger at extended arms length and close one eye. Then switch and close the other. The point of your finger will shift. Parallax only works with nearby stars but the more the stars shift the closer it is. Concept 2: Arc minutes -‐ You are really measuring an angle when you’re measuring how something shifts. In astronomy you measure angles by arc minutes. There are 360 degrees in a circle. 1 degree = 60 arc minutes One arc minute can be divided up into 60 pieces to be called an arc second. Si second duration of 9129631770 periods of radiation given off by hyperfine transition cesium 133 Mass – SI kilogram – standard kg located in France Solar mass = mass of the sun Chapter 2: The Night Sky General patterns in the sky… (Chapter preview) There are patterns of motions in the sky The sunrises and sets (so does everything else…moon, stars, planets, etc.) The circling sky is a result of the rotation of the earth on its access The orbit of the earth around the sun combined with the earth’s access tilt is also the reason for seasons. The moons orbit around the earth causes it to go through different phases. The ancient mystery of the Planets – the various orbits around the sun. Day – earth’s access Week -‐ planets’ orbit – Mercury, Venus, Mars, Jupiter, moon, sun. The 7-‐day week was created named after those objects^ Month -‐ the moon’s orbit around the earth Year -‐ the earths orbit around the sun Constellations: A region of the sky, within official borders set in 1928 by the IAU Often recognizable by a pattern or grouping of stars - Constellations, while interesting, are not really of that much use in astronomy. Astronomy is more concerned with borders of constellations. So stars that do not constitute the stick figure of Orion are still considered part of that constellation if they fall within the set borders. To us the sky looks like a hemispherical screen. We can only understand and see a 2 dimensional view of a 3d universe. So when you look up you perceive stars and planets to be close together but that’s not necessarily the case. There are coordinates in the sky just like there are coordinates on the earth Coordinates on the earth: Latitude is where you are north and south referencing the equator Longitude – prime meridian is in Greenwich England. (We are west of the prime meridian) Sphere of the sky is called the celestial sphere – obviously in real life the universe is not a sphere – but that’s what they used to believe. So even though it’s not a physical reality it’s useful to describe what we see. And we can apply the same latitude longitude concepts to describe the night sky (picture earth sitting smack in the middle of another sphere) Reference slide for photo Take earth’s equator and move it out that becomes the celestial equator. Same thing for the celestial poles Ecliptic – a word we use for the path that the sun takes around the celestial sphere
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