AST 10G Study Guide - Midterm Guide: Parsec

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Published on 10 Sep 2016
School
UC-Davis
Department
Astronomy
Course
AST 10G
Professor
AST10GStudyGuideforMidtermI(bychapter)
Chapter1:OurPlaceintheUniverse
Knowour"cosmicaddress"(solarsystem,theMilkyWay,theLocalGroup).
Solarsystem=Sun,planets,moons,asteroids,comets
MilkyWay=galaxy,oursolarsystemislocatedhalfwayfromcentertotheedge
LocalGroup=40galaxies,MilkyWayisoneofthe2largest
Knowtheunitsformass,distance,size,time,speed/velocity,angularsizethatweuseinastronomy.
Mass=measuredinsolarmassbasedonoursun,1solarmass=1.99x1030kg
Distance=measuredinastronomicalunits,1AU=distancebetweensuntoEarth=1.5x108km
Parsecs=3.09x1013km
Time=Lightyears,distancelighttravelsinoneyear,3x105km/s
3.26lyrs=1parsec
1lyr=9.46x1012km
Speed/Velocity=measuredthroughDopplershiftoflight,v=c(wavelengthresting
wavelength)/restingwavelength
Angularsize=measuredindegrees,arcminutes,andarcseconds,1degree=60arcminutes,d=
(a/360)x2πR=aR/57.3
Knowhowthesizesofthefollowingrelatetoeachother:sizeofplanetsrelativetoSunandeachother,
distancesbetweenplanets,thesizeofthesolarsystem,distancesbetweenstars,sizeoftheMilkyWay
andothergalaxies,distancesbetweengalaxies.
EarthtoSun:1AU
MarstoSun:1.5AU
PlanetstoPlanets:planetsaresmallerthanthedistancesbetweenthem
DistancebetweenPlanets:measuredinAU
SolarSystem:verylarge,cannotbemeasuredinkm
DistancebetweenStars:measuredinparsecs,closeststartoEarthis1.3pc
MilkyWaytoOtherGalaxies:1mpc
DistancebetweenGalaxies:megaparsecs,millionsoflightyears
 
Knowroughlyhowfastthingsaremoving(Earth'srotation,thesolarsystemintheMilkyWay,galaxies
ingroupsandclusters).
Earth’srotation=200km/s
SolarsystemintheMilkyWay=starsrelativetootherstars=10km/s
Galaxiesingroupsandclusters=1,000km/s
ChapterS4.2:BuildingBlocksoftheUniverse
Knowaboutthefourfundamentalforcesofnatureandwhichisthemostimportantforastronomy.
Gravity=theforcethatkeepsthingsfromgoinginastraightlineandkeepsastronomicalobjects
boundtogether,dependsonmassesofobjectsandseparation,attractive
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Electromagnetic=attractiveorrepulsive,onlyworksbetweenparticleswithelectricalcharge,in
proportiontotheamountofcharge
StrongNuclear=strongestofallforces,overcomesrepulsiveelectromagnetismofprotons
WeakNuclear=responsibleforradioactivityandparticledecay
Chapter4:MakingSenseoftheUniverseUnderstandingMotion,Energy,andGravity
Whatisaforce?
apull(attraction)orpush(repulsion)thatcausesthedirectionand/orspeedofmotiontochange
→changeinvelocity→acceleration
F=m•a
Whatisanacceleration?
changeinspeed/direction
Knowtheunitsforforce,acceleration,mass,velocity.
force=kg•m/s2
acceleration=m/s2
mass=kg
velocity=m/s
Knowthedifferencebetweenmassandweight.
weight=mass•gravity
massistheamountofmatterinsomething
UnderstandNewton'slawsofmotionandtheirimplications.
Newton’s1stLaw:anobjectatreststaysatrest,anobjectinmotionkeepsthesamedirection&
speed
Newton’s2ndLaw:forcesmakethingsmovebyacceleratingthem
Understandthelawofconservationofmomentum.
Thetotalmomentumofasystemisconserved
Understandthelawofconservationofenergy.
energycannotbecreatedordestroyed,onlytransformedfromoneformtoanother
Understandthedifferentformsofenergy.Beabletogiveexamplesofdifferentkindsofpotentialenergy
besidesgravitational.
Kinetic=heatorthermal,rapidlymovingparticles
Gravitationalpotential=PE=G•m1m2/d
Chemicalpotential=energyreleasedbybreakingchemicalbonds
Mass=anythingwithmasshaspotentialenergy,E=mc2
 
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