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Astronomy 1020 Fall Exam Review

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Western University
Astronomy 1021
Carol Jones

Astronomy 1021 Review Lecture 1: Order from Earth to Local Supercluster: - Earth - Solar System - Milkyway Galaxy - Local Group - Local Supercluster How did we get here? : - universe begins and expands - galazies form - stars from & die, make elements - planets & life froms Star: - large, brigh ball of gas - generates heat and light thorugh nuclear fusion - creates its own heat and light Planet: - moderately large object that orbits a stat - shones by reflected light - made of rock, ice or gas (or some of each) Moon (or satellite): - an object that orbits a planet - Jupiter has approx. 20 moons Asteriods and Comets: - small objects orbiting a star - not round - asteroids: rocky - comets: icy - comets are made up of a lot of material like rock, ice, ect. - dust tail and plasma tail - tail always points away from the sun due to radiation and pressure and the residue left from the comet is ionized Solar System: - a star and all orbiting material - included its planets and their moons Nebula: - an intersteller cloud of gas and/or dust - planetary nebula: small star in dying phase Galaxy: - an "island in space" held together by gravity - stars and their corpses - gas - dust, planets - dark mater (we don't know much about it) Universe: - everything - sum total of all matter and energy - everything within and between all galaxies How can we know what the universe was like in the past? - Light travels at a known speed (300,000 km/s) - So we see objects as they were in the past: - farther away in distance ----> further back in time - Moon = 1 second - Sun = 8 minutes - nearby star Sirius = 8 years - Andromeda Galaxy = 2.5 million years - for example, we have to wait 2.5 million years to see what the Andromeda Galaxy looks like now Light Year: - distance light can travel in one year - about 10 trillion km Lecture 2: - one lightyear is = 9.46 x 10^12 km - therefore one lightyear = 9,460,000,000,000 - there are about 10^22 stars in the observable universe - the Milky Way is one of about 100 billion galaxies - if we assume there are about 100 billion stars in each galaxy... - # of stars/galaxy x 10^11 galazies = 10^22 stars - as many stars as grains of dry sand on all Earth's beaches - the milky way galaxy is about 10^5 light-years across and 10^3 light years thick - distance, velocity, and time are related - v=d/t, or d=v x t, or t = d/v - example: driving for 3 hours (time) at 20 km/h (velocity) = 60 km (distance) - the earth-sun distance is also called an astronomical unit (AU) - earth is moving pretty fast, starting with its own rotation - the earth rotates around its axis once every day - apprx. 1700km/h - earth orbits the sun once every year - rotation and orbitial directions same - rotation axis tilted 23.5 degrees compared to orbital plane - galaxies are carried along with the expansion of the universe - all galzxies outside our local group are moving away from us - the more distant the galaxy, the faster it is racing away Lecture 3: How big is Earth? : - if you reduce the solar system by factor of 10 billion... - the sun would be the size of a large grapefruit - the Earh would be the size of a ball point - radius of earth = 6371 x 10^3m - Sun - Mercury - Venus - Earth - Mars - Jupiter - Satern - Uranus - Neptune - Pluto - our solar system would be the size of UWO campus How big is the Milkway Galaxy? - 100000 light years across - the milkway would be the size of a soccer field (at a 1:10^19 scale) - latitude and longitude are both angles - latitude is a side view - longitude is when your on top of the north view - prime meridan = straight longitude line - eqautor = the straigh
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