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Astronomy 1021 Study Guide - Final Guide: Virgo Supercluster, Planetary Nebula, Local Group

Course Code
ASTR 1021
Carol Jones
Study Guide

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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
- large, brigh ball of gas
- generates heat and light thorugh nuclear fusion
- creates its own heat and light
- 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

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- an intersteller cloud of gas and/or dust
- planetary nebula: small star in dying phase
- an "island in space" held together by gravity
- stars and their corpses
- gas
- dust, planets
- dark mater (we don't know much about it)
- 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)
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