second midterm notes
DepartmentAstronomy & Astrophysics
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White light-mixture of basic colored light in equal proportions. Black=no light, no color
Emission-eg.light bulb,energy of light comes fr electricity potential energy.
Absorption-eg.cover light bulb w/ hand,hand absorbs some light&this energy makes hands warm.
Transmission-eg.glass,air allows light to pass through.
Reflection/scattering-light bounce off matter,reflection-same direction. Scattering-random direction
wave-wavelength, frequency, period.c=f*wavelength, Particles-thing Wave-pattern revealed by p.
Light-Electromagnetic waveconsists of individual photons characterized by wavelength,frequency&
energy.Speed is constant.-both wave&particles.
Electomagnetic spectrum-Gamma rays-Xrays-ultraviolet-visible-infrared-radio.
Atoms-protons, neutrons,electrons,nucleus. Atom#=proton# Atomic mass#=#of protons=#neutrons
Isotope-elements w/ different# of neutrons. Atoms-molecules-compounds
Phases-solid,liquid,ice.-Chemical bonds stronger-tighter-sold , if weaker, then liquid, gas
-eg. Water- Sublimation-escape solid Evaporation-escape liquid
-Molecular dissociation-high temp->molecule collide->break bonds->lose electrons->ionized
-Plasma-type of gas which atoms have become ionized. eg. Sun is made of plasma/hot gas
Pressure-force per unit area. Earth core is solid cuz of pressure, tho its temperature is high.
Energy level transition-as electron rise fr low energy level to higher one/fall fr high to low.
Spectroscopy-obtain spectrum&read info.display graphs showing intensity at diff. Wavelengths.
-Continuous spectrum-broad range of wavelengths w/out interruption.
-Emission line spectrum-low density clouds emits light only at specific wavelengths. Depends on
composition&temperature. Emission lines against a black background.
-atoms in cloud collide bump electrons to high energy level,then fall back
&loses energy by emitting photon of light at specific wavelength.
-Absorption line spectrum-cloud lies b/w source&us, still see most continuous light,cloud absorbs
some at specific wavelengths. Dark absorption lines over rainbow.
-as atoms absorb light,electon fr high leve return to low level&emits a
photon of same energy absorbed but goes to random directions.
Chemical Fingerprint-elements emits/absorb light at diff wavelength, by observing spectrum,unique
patterns can determine wat element. Ions cud help determine temp.->high
temp-more highly charged ions. Molecules-create spectral lines wen electron
change energy level/vibration/rotation.Tightly brunched lines-molecular band
Thermal Radiation-atoms&molecules in objects r not independent, have complex energy levels->
absorb light across broad range of wavelengths.as absorb photons,photons try to
escape, its quickly absorbed by atom/molecule->reemits photon at diff wavelen.
&direction->photons bounces randomly->constantly exchange energy->when it
finally escapes,the radioactive energies spread over wide range of wavelengths
->produce continuous spectrum--Only depends on temperature->rep.avg.kinetic e.
-Two laws-1.Each square metre of hotter objects surface emits more light at all wavelength.
2.Hotter objects emit photons w/ higher avg. energy (shorter avg. wavelengths)
-estimate star's temp. by observing its color. Eg.ppl-infrared star-red-3000k.
-reflected light gives color, absorbed light heat the surface &help determine temp.
Doppler effect-Blue shift-Object move toward us,waves bunch up b/w us&object,shorter wavelengh
-Red shift-object move away fr us,light is shifted to longer wavelength.
Only when object is moving directly away fr. Us we know full speed.
Comparative planetology-compare to one another,find similarities/differences.
Sun-helium+hydrogen. Sun spots are cooler areas. Solar storms->send streamers of hot gas above
surface. Loses 4 million tons of mass/sec,will shine for another 5 billion yrs.
Mercury-Smallest among eight.-not active, no wind. Both hot and cold extremes. Heavily cratered.
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Venus-size nearly identical as Earth, rotates slow&opposite direction of Earth. Dense clouds->
extreme greenhouse effect->hot as pizza oven.
Mars-frozen CO2,evidence of river beds etc.
Jupiter-mass 300xEarth. Volume1000x. Many moons, faint rings. Great red spot-long lived storm
-no solid surface. Helium&Hydrogen. 4 Galileon moons-Io-volcanic Europa-icy
Saturn-lower density less massive. Helium&Hydrogen gas ,no solid surface. Rings-countless small
particles orbits Saturn. Spacecraft-cassini goes there to observe Saturn.
Uranus-H,He,H2O ammonia&methane.-Blue. Lack solid surface. Tipped on side-extreme season v.
Neptune-More blue. Moon (Triton) orbits backward.
Pluto-dwarf planet.ice+rock. Different class.located in Kuiper belt.
Patterns of motion among large bodies-planetary orbits nearly circular&lie nearly in same plane
-planets orbit sun in same direction(counterclockwise)
-most planets rotate in same direction in which they orbit,w/
small axis tilt.(including sun)
-moon orbits planet's equatorial plane.
Two types of planets-terrestrial planets-four inner planets-small,dense,rocky surface,metals in cores
few moons,no rings.
-jovian planets-four larger planets.low density,rings,numerous moons,Helium
hyrogen,ammonia, methane.gas giants.
Asteroids&comets-vast numbers,orbit sun.Asteroid-rocky, small, found w/in asteroid belt. Comets-
ice&rock,beautiful tails, few visit inner solar sys.and remain far fr sun w/out tails
-kuiper belt-beyond orbit of Neptune,contains 100000icy objects, oort cloud-
Exception to the rule-Uranus rotates almost on its side,Venus rotates backwards,some moon have
unusual orbits, Earth has a large moon.
Flyby-goes past world once and continue on its way. Obiter-orbits the world ,allow long-term study
Lander/probe-land on planets surface. Sample return mission-returns to Earth carrying sample.
Nebula theory-solar sys born fr a cloud of gas(solar nebula),collapsed under gravity. It began as a
large spherical cloud,cold, low-density gas,spread out in few light-yrs diameter,as it
collapse,shrank in size.3 processes altered density,temp,shape,cloud->spinning disk
1Heating-temp of solar nebula increase,shrank->gravitational potential energy->kineti
ic energy of gas particles,collide-> thermal energy, sun formed->highest temp&dense
2Spinning-solar nebula rotate faster as it shrank in radius->conservation of angular
momentum.more the momentum, more spread out it wud be, not everything in centre
3Flattening-natural consequence of collision b/w particles in a spinning cloud,
Testing model-heating occurs->gas emit thermal radiation-we detected infrared radiation.
Why two types of planets?particles condense out of gas form planets. Ingredients in solar nebula:
-Hydrogen&helium gas;Hydrogen compounds(condense into ice beyond frost line);Rock;Metal.
-Frost line-distance which is cold enough for ice to condense.marks transition b/w warm/cool region
inside frost line only metal&rocks condense,beyond-hydrogen compound condense
Terrestrial planets form-accretion-microscopic particles orbit around sun,collide with neighbor,but
too small to attract each other,they cud stick tog thru electrostatic forces->
same as “static electricity”(hair stick to comb)->small particles->big ones->
gravity aids and form planetesimals(pieces of planets).
Jovian planets form-Accretion,but more amounts of ice than rocks and metals.had more gravity.
Wat ended planet formation-most gases swept into interstellar space by radiation fr sun&solar wind.
Sun rotates slow now->because of solar wind swept particles away->lose angular momentum.
Where asteroids&comets come fr?-as sweep excess gas fr solar nebula,many planetesimals remain
scattered,leftovers become asteroids/comets.Asteroids are rocky
leftovers,comets-ice rich,some qualify as dwarf planets.
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