lec 2 universe, galaxy, solar aug 11, 2010

8/8/2019 Lec 2 Universe, Galaxy, Solar Aug 11, 2010

1/42

Universe

Cosmology

Big Bang Theory

Stars

GalaxiesMeteorites

Comets

Asteroids

Black Hole

Aurora

The Solar System


2/42

Cosmology

A branch of Astronomy.

study oftheuniverseasa whole, past &

future. Observational looking attheuniverse.

Theoretical Physical Lawsand Theories


3/42

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


4/42

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.


5/42

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.


6/42


7/42

Starscont..

Definition:

A Massiveshining sphere ofhot gas.

Composition: Madechiefly ofhydrogenandsmall amounts of

helium.

Oxygen, Carbon,neon,nitrogenvery small. Youngerstarscontainhigher proportion of

metalsandheavy elements.


8/42

Starscont

Formation:

Compression wavestravelling through large

gas (hydrogen)cloudsmake gas knots. Gravitational pull makes knotsdenser.

Morecompression increasedtemp.

Nuclear fusionstarts. A new star!


9/42

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)


10/42

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.


11/42

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.


12/42

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


13/42

Galaxy cont..Spiral Galaxy - Andromeda


14/42

Galaxy cont..

Elliptical Galaxy M86 / M84


15/42

Meteorites

A small chunk ofmatter floating inthespace

thatcanenterany planetsatmosphere.

Outside Meteor

Whenentersintheatmosphere Meteorite.

Hoba west (Nambia) 1920

Cape York (Green Land) - 1894


16/42

Comets

Small,icy celestial body revolving aroundthe

sun.

Whenacometnearsthe Sun,some oftheice

inthecometturnsinto gas. The gasand loosedust freed fromtheicecreatea long,

luminoustail thatstreams behindthecomet.


17/42

Cometscont


18/42

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.


19/42

Asteroidscont..


20/42

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.


21/42

Black Holecont


22/42

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.


23/42

Auroracont


24/42

Solar System

Definition:

The Sunandthecelestial bodies orbiting the

Sun,including thenine planetsandtheir

satellites;theasteroidsandcomets;andinterplanetary dustand gas.

4.6 thousandmillion years old.


25/42

Solar Systemcont


26/42

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


27/42

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.


28/42

Planets

Mercury: Orbitscloserto sun;dry,hotandairless.


29/42

Planetscont

Venus: Brightest objectinsky aftersunandmoon.

Covered by sulfurclouds;surfacetemp. 4600 C.


30/42

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.


31/42

Planetscont


32/42

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


33/42

Planetscont


34/42

Planetscont

Jupiter:

Largest planet;volume 1400 times greaterthan

earth. Colourfull dueto lightanddark bands ofclouds.

Only coreisrocky,restisall liquidmainly

composed ofhydrogenandhelium.

Ithas 4 moons.


35/42

Planetscont


36/42

Planetscont

Saturn:

Sixth planet fromsun.

Distinguished by beautiful rings. Second largestafter Jupiter.

Composed ofhydrogen & helium.


37/42

Planetscont


38/42

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.


39/42

Planetscont


40/42

Planetscont

Neptune:

Slightly smallerthan Earth.

Bluish planet with parallel cloud beltsandhigheraltitudemethaneclouds.

Ithaseightmoons.

Atmospheremadeup primarily of Nitrogen.


41/42

Planetscont


42/42

Planetscont

Pluto:

Farthest from Sun.

Composed ofamixture ofrock andice. Diameter only 2300 Km.

Temp. below -2100 C.

Surfaceis believedto becovered withmethane.

lec 2 universe, galaxy, solar aug 11, 2010

Documents