AST 10G Study Guide - Final Guide: Recessional Velocity, Nucleosynthesis, Office Of Gas And Electricity Markets

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Published on 10 Sep 2016
School
UC-Davis
Department
Astronomy
Course
AST 10G
Professor
Chapter19:OurGalaxy
StructureoftheMilkyWay(disk,bulge,halo)
Characteristicsofeach,includingstellarpopulations,color,spatialextent(size)
madeupof100billionstars
spiralgalaxy
surroundedbydimhalo
center=bulge
dustallaroundit
What'sfoundwhere?Forexample,globularclusters,starformationregions,spiral
arms
StarGasStarcycle
atomichydrogenclouds→molecularclouds→starformation→nuclearfusion
instars→returninggas→hotbubbles
MolecularClouds
Whyionizationnebula(HIIregions)formwherestarformationisgoing
on;whatproducesemissionofdifferentwavelengths(orwhyarethe
regions"colorful")?
HIIregionsformbecauseofionizationduetohotyoungOandB
stars
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regionsarecolorfulduetostrengthofemissionlines
Howstarformationproceeds?O&Bstarassociationsandhowdothey
affectthemolecularcloud?
O&Bstarsarebadbecausetheyaresohottheyionizethegas
aroundthemandcreateemissionlines
eatawayatthemolecularcloudthatformedthem
Appearanceofstellarpopulationsofdifferentages(HRdiagrams,etc)
younger=bluer=hotter
older=redder=cooler
OBAFGKM
Supernovae(SNe)SNremnants&ejectedmatter
Chemicalenrichmentofgalaxies(primordialelementratiosversustheMilkyWay
"metallicity"now)
waymoreelementsthanoriginallypresent
heavierelementspresentduetocontinuedfusion
Shockwaves
createsHIIgas(ionized)
ComponentsoftheISMinourgalaxy
Hot,warm,cold(molecular)gas
Cold,dense,tightlyclumpedH2,starsformwithin
Cool,lessdense,lessclumpedHI,mostcommonphase,formationofnext
generationofstars
Hot,morediffuse,IonizedHII,byproductofformingyoungstarsand
supernovashockwaves
Dust
madeofCandSiparticles
scattersbluelight,letsredlightthrough
blockslightsomakesgalaxiesappeardimmer&redder
Stars,stellarremnants
siteswherestarsform
starsformindensestpartsofcloud
Howdowestudyeachofthesecomponents?Forexample,wavelengthsof
radiationthateachcomponentemits,bestwavelengthstoobservethecomponent,
etc.(seeTable19.1andFigure19.12)
HIdetectedthrough21cmradiation:21cmlineeasilydetectablewith
radiotelescopes
radiomaps:shortwavelengthsabsorbed,wavelengthsofsimilarlengthget
scattered,longwavelengthsgothrough
GalacticEnvironments
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Diskpopulations
containsbothyoungandoldstars
heavyelementproportionsofabout2%
Howwouldyourecognizeastarformationregion?
gasclouds
heavyelements
StellarmotionsintheMilkyWayandwhatthattellsyouabouthowtheMilky
Waymighthaveformed
giantprotogalacticcloudofhydrogenandheliumgas
muchofthegascontractedandfragmentedduetogravity
remainingglassettledintoaflattened,spinningdisk
starsformedwithinthediskbecamediskpopulation
couldalsohavebeenformedfrommergerofsmallerstarsystemsformed
frommultipleprotogalacticclouds
PositionofthesunintheMilkyWay
canstudycurrentstarformationregionsthroughHemissionline
luminosity
Ultravioletluminosity
FarInfraredLuminosity
26,000lyfromthecenterofthemilkyway
Rotationcurveofourgalaxyandwhatitmeans
rotationcurve=plotofrotationalspeedasfunctionofdistancefromthe
centerofthegalaxy
ThevelocitydoesNOTfallwiththeradiusmeaningtheremustbemore
andmoremassatlargerradii→darkmatter
Massinsideandoutsidethesolarcircle
inside=100billionsolarmasses
outside=twiceasmuch
Spiralarmswhattheyareandhowdotheyform?(stellarpopulationsinthem,
thedensitywaveidea,etc)
formedbyspiraldensitywaveakadisturbanceingalaxies
starformationinspiralarms:gascloudscollideindensestpartofwave,
densemoleculargasisformed→stars
Galacticcenterregion
What'sthere,whatemissionwesee,whatcausestheemission,whatistotalmass
inthecentralobject,howdowemeasurethismass?
swirlingcloudsofgasandaclusterofseveralmillionstars
magneticfields
inthecenterisasourceofradioemissionnamedSagittariusA*
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