lec 2 universe, galaxy, solar aug 11, 2010
TRANSCRIPT
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Universe
Cosmology
Big Bang Theory
Stars
GalaxiesMeteorites
Comets
Asteroids
Black Hole
Aurora
The Solar System
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Cosmology
A branch of Astronomy.
study oftheuniverseasa whole, past &
future. Observational looking attheuniverse.
Theoretical Physical Lawsand Theories
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Big Bang Theory
currently acceptedexplanation ofthe
beginning oftheuniverse.
Universe onceextremely compact,dense,hot.
Big Bang 10 to 20 Billion yearsago.
History
Based on fieldequations ofthe general theory
ofrelatively given by Einstein 1915
1922 - Alexander Friedmanns set ofsolutions
to fieldequations basis of further work
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Big Bang Theory Cont
1929 Edwin Hubble proved galaxiesare
moving away fromeach other Uniform
Expansion.
1948 George Gamow predictedthatecho
from big bang canstill beheardinthe form of
cosmic backgroundradiation.
1965 Penziasand Wilsondiscoveredthe
cosmic backgroundradiation.
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Big Bang Theory Cont
The Theory
Whathappenedat orsoonafterthe beginning of
universe.
Universeexpandedrapidly in firstmicroseconds.
Slowerexpansion later on.
Openmodel universe will keep expanding
forever.
Closedmodel universe will stop expanding and
begincontracting until itcollapses.
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Starscont..
Definition:
A Massiveshining sphere ofhot gas.
Composition: Madechiefly ofhydrogenandsmall amounts of
helium.
Oxygen, Carbon,neon,nitrogenvery small. Youngerstarscontainhigher proportion of
metalsandheavy elements.
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Starscont
Formation:
Compression wavestravelling through large
gas (hydrogen)cloudsmake gas knots. Gravitational pull makes knotsdenser.
Morecompression increasedtemp.
Nuclear fusionstarts. A new star!
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Starscont
Characteristics:
Magnitudeisthemeasure of brightness. 6 classes
ofmagnitude. 1st magnitudeisthe brightestand
2nd magnitudeis 2.5 times less brighter.
Luminosity isthetotal energy radiated/second
withreferenceto sun.
Colour usually correlates withtemp. Blueveryhot, White little less (10,000 C), yellow (oursun
6000 C)andred (3000 C)
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Starscont
Types:
Can beclassifiedinto kinds.
Fixed do notaltertheir position.
Binary group oftwo revolving aroundcommoncentre.
Temporary suddenly increase brightnessandthenfadeaway.
Variable brightnessvaries fromtimeto time. Red giants consumed 10% ofhydrogen.
Whitedwarfs laststage ofred giantsafter
consuming all hydrogen.
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Starscont
Super Nova anexploding starshining brieflyandas brightly asathousandmillionstars.
Nebula A region ofdustand gasin galaxy,
consideredaremnant ofsupernova. Quasars Distantanduniversally bright
objects;considerednuclei ofactive galaxies.
Protostars Patches of gasanddustinnebula
forming dark regions which laterturninto star.
Pulsar Rotating neutronstaremitting regular
pulses ofradiationappearing as flashes of light.
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Galaxy
Definition: Fundamental unit ofuniverse.
Several hundredthousands ofstarstogether withinterstellar gasanddust.
Classification:
Edwin Hubbleclassified galaxiesinto 3 categories
Spiral flatteneddisk likesystem withspiral arms
ofcloudsandstars.
Elliptical Overall globularshape.
Irregular neitherspiral norelliptical
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Galaxy cont..Spiral Galaxy - Andromeda
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Galaxy cont..
Elliptical Galaxy M86 / M84
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Meteorites
A small chunk ofmatter floating inthespace
thatcanenterany planetsatmosphere.
Outside Meteor
Whenentersintheatmosphere Meteorite.
Hoba west (Nambia) 1920
Cape York (Green Land) - 1894
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Comets
Small,icy celestial body revolving aroundthe
sun.
Whenacometnearsthe Sun,some oftheice
inthecometturnsinto gas. The gasand loosedust freed fromtheicecreatea long,
luminoustail thatstreams behindthecomet.
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Cometscont
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Asteroids
Small,rocky planetoids.
Members ofthesolarsystem.
Revolveinelliptical orbits primarily between
the orbits of Marsand Jupiter.
Believedto beremnants of former planets.
Asteroidsintersecting Earths orbitare known
as Apollos.
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Asteroidscont..
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Black Hole
Definition: A theoretical,extremely densecelestial body.
Very strong gravitational field noteven lightcanescape.
Formation:
Very largestar whenruns out of fuel,startscollapsing onitself.
Thesmallerit becomes,more gravitational pullitexertsandvanishes fromsight.
Becomesextremely small and powerful.
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Black Holecont
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AuroraDefinition:
Luminousatmospheric phenomenon.
Frequently occurs 60 0 north orsouth latitude.
consists ofrapidly shifting patchesanddancing
columns of light ofvarioushues. Aurora Polaris (polar lights) - general name.
Causation:
Charged particlesinsolar windsentereartharoundpoles. Earthsupperatmosphere getscharged withaccess protons & electrons. These particlescolloidwith gasandemitradiation.
Thisvisibleradiationiscalled Aurora.
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Auroracont
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Solar System
Definition:
The Sunandthecelestial bodies orbiting the
Sun,including thenine planetsandtheir
satellites;theasteroidsandcomets;andinterplanetary dustand gas.
4.6 thousandmillion years old.
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Solar Systemcont
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The Sun.
Hugedynamic globe of gas.
Diameter 1.4 million km big enoughto
contain 1.4 million bodies ofsize ofearth! Madeup ofhydrogen (73%),helium (25%).
Generatesenergy by nuclearreaction
converting hydrogeninto helium. Surfacetemp. around 5500 0 C
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Planets
Nine Major planetsarecurrently known. Inner planets - Mercury, Venus, Earth, Mars;
relatively small andcomposed primarily ofrock
andiron Outer planets - Jupiter, Saturn,Uranus,
Neptune;much largerandcomposed of
hydrogen,heliumandice.
Pluto doesnot belong to any group.
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Planets
Mercury: Orbitscloserto sun;dry,hotandairless.
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Planetscont
Venus: Brightest objectinsky aftersunandmoon.
Covered by sulfurclouds;surfacetemp. 4600 C.
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Planetscont
Earth: Oxygenrichand protectiveenvironment.
Moderatetemp. supports life.
3rd
planet fromsunand 5th
largest. Avg. distance from Sunis 150 million km
Earthscoreiscomposed ofmoltenrock andmetal;surrounded by denserock (mantle) &thincrust.
Surfaceis formed by sectionscalled plates.
Life beganapprox. 3500 million yearsago.
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Planetscont
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Planetscont
Mars:
4th planet fromsunatadistance of 228 million km
Halfthediameter ofearth; 1/10 ofearthsmass Avg. surfacetemp. -550 C
Calledred planetdueto colour whichis because
ofiron oxideinitssoil. Marshastwo moons Phobos andDeimos
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Planetscont
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Planetscont
Jupiter:
Largest planet;volume 1400 times greaterthan
earth. Colourfull dueto lightanddark bands ofclouds.
Only coreisrocky,restisall liquidmainly
composed ofhydrogenandhelium.
Ithas 4 moons.
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Planetscont
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Planetscont
Saturn:
Sixth planet fromsun.
Distinguished by beautiful rings. Second largestafter Jupiter.
Composed ofhydrogen & helium.
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Planetscont
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Planetscont
Uranus:
Firstto bediscoveredthroughatelescope
1781 by William Hersschel 3rd largest planet; 4 timessize ofearth.
Besideshydrogenandheliumithas Methane
gashence,the blue greencolour.
Temp. below -185 0 c.
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Planetscont
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Planetscont
Neptune:
Slightly smallerthan Earth.
Bluish planet with parallel cloud beltsandhigheraltitudemethaneclouds.
Ithaseightmoons.
Atmospheremadeup primarily of Nitrogen.
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Planetscont
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Planetscont
Pluto:
Farthest from Sun.
Composed ofamixture ofrock andice. Diameter only 2300 Km.
Temp. below -2100 C.
Surfaceis believedto becovered withmethane.