Descriptive Astronomy The Solar System
Descriptive Astronomy The Solar System ASTR 26300
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THE COSMIC LANDSCAPE 82310 Astr is the physical science that studies inaccessible ET objects It s an observational science not experimental Planets don t produce energy they receive it from the stars Stars are the energy producers The moon is a natural satellite of the Earth Mi the size of the Earth 1 ofa million miles away My Very Educated Mother Iust Served US Nine Pickles Terrestrial First 4 All are rocks Iovian Last 4 The Sun Average star in size temp mass It is 300000 X s greater than Earth It has a diameter of over 100 X s that of Earth The Solar System 82510 Everything under the gravitational pull of the sun all planets and asteroids comets all natural satellites The astronomical unit AU is defined as the average distance from the earth to the sun It is equal to 150000000 km or 93000000 miles Venus and Earth used to be called the sister plants Russians sent a probe to Venus to transmit info but the electrons melted The temp was hotter than the melting point oflead because of global warming Mars could have had H20 in the past Jupiter is all gas Iupiter Saturn Uranus Neptune have rings Merc V E Mars are al tiny 1st star is 43 light years away Milky Way is our particular galaxy Contains about 100 billion stars Looks like a dinner plate Light year distance light would travel in 1 year Has the speed of186000 milessecond In one year it would travel 6 trillion miles Sun is located 28000 LY from the center Rotation period is 240 million years Milky way is a part ofa cluster of galaxies called the local group 30 galaxies This cluster is part of an even larger cluster called super clusters We are called the local super cluster which contains a few dozen clusters of galaxies and is about 100 million LY in size Purpose ofscience to understand nature sufficiently well to enable a successful prediction of future events on the basis ofpast and present events quotOckham s Razor William Ockham 1349 AD Cut away until you have the simplest representation of nature consonant with the known facts Mathematical models are used to make predictions in science The models may not look like nature but they are very useful in describing and making predictions Scientific method CHAPTER ONE Prehistoric Astr Archaeologists have found bones with marks on them that they believe rep some type of astronomical calendar 25000 years old Stonehenge 2000 to 3000 BC The Great Pyramid at Giza several thousand BC seems to indicate that the builders had a rather detailed knowledge of the sky The Celestial Sphere Earth in the middle infinite radius all stars located on the surface of the sphereGood model shows no reality Constellations 1928 International Astronomical union defined as the boundaries of 88 constellations they have no physical significance The north and south Celestial poles are where the rotation axis of the Earth intersects the celestial sphere The North Star is very near the North Celestial pole Celestial equator is Earth s equator extended to infinity Zenith point directly above you changes depending on where you are Nadir point is 180 degrees below your feet Meridian great circle on the celestial sphere that passes through the poles and observer s zenith The angular distance of Polaris with your northern horizon is equal to your latitude in the n hemisphere Stars which are located an angular distance less than your latitude from Polaris will never set 0 They are called Circumpolar stars Astronomers will use universal time the time in Greenwich England Orbital period of Earth is 365242 days we gain a day on leap year Since 242 isn t exactly 14 only centuries divisible by 400 are leap years Diurnal motion daily motion of starsamp sun in the sky Annual yearly motions of the stars and sun across the sky The ecliptic is the apparent path of the sun over one year In reality we the earth are the ones moving The great circle of the ecliptic makes an angle of 235 degrees with the celestial equator ce known as the obliquity oftbe ecliptic Vernal equinoX intersection of the ce and ecliptic as the sun moves south to northern hempMarch Spring Autumnal equinox intersection of the ce and ecliptic as the sun goes north to south Sept 2 2 2 3 Fall Equinox means equal day and night Winter solstice sun is farthest south Dec 21 winter Summer solstice sun is greatest distance north June 21 summer In the winter Earth is closest to the sun because the obliquity perpendicular of the ecliptic The tilt is what matters not the distance to the sun 9110 The Arctic Circle lat 665 N gets 24 hours of daylight at the time of the summer solstice Tropic ofCancer lat 235 N has the sun located at the zenith at the summer solstice Tropic ofCapricorn 235 S Antarctica Circle Zodiac band of constellations through which the sun moonampplanets appear to move in the course of 1 yr 0nean Solar time time intervals between successive passages of the mean 0 3 min and 56 seconds longer than a sidereal day Sundial measures the true solar day Difference between true and mean solar day referred to as the equation of time Difference varies between 142 and 163 minutes Solar day is NOT equal to sidereal day Earth rotates itself and then it also rotates around the sun Earth wobbles called precision Takes 2600 years to complete one precision spin means Polaris won t always be the North Star THE MOON 9810 Natural satellite orbiting earth Goes through phases Exactly 180 degrees apart Solar eclipse Sun shining then here s the moonthen the earth is over here so the sun can t get to the earth there are 2 a year with a max of 5 Lunar eclipse sun shiningthen here s the earththen the moon max of 3yr min of 0 Lunar are more common In order for an eclipse to occur the moon s orbital plane must intersect the sun then we have a eclipse seasons The precision period is 186 years They don t occur the same date and there are a possibility of 7year CHAPTER 2 Pythagoras 560480 BC said earth was a sphere no hard facts to support it Aristotle said during a lunar eclipse you see a shadow so earth must be a sphere because of the shadow Also said ifyou look at a star in the sky that s just above the horizon then walk some other place it s now moved positioning el s 276195 BC measured size of earth using some elegan me simple observa 39ons Lived in Egypt lat 31 10N Realized June 21 Summer solstice the sun at Syene w nearly at the zenith of the moon Had some random guy measure the distance between the two by looking at the shadows The guy who did the measuring said the distance between these two places must be 150 of the distance around the entire earth 0 This distance was 500 So the circumference but by 50x s this value or 25000 He was extremely right the real distance is 24902 Aristarchus moon is approx 35 the size of earth Parallax This is what happens when you line your finger up with some thing Stars are so far away that the parallax angels are very small and can t be detected with the naked eye Ian B C Celestial motions quotplanetquot comes from the Greek word wanderers Geocentrl39c System most logical idea that everything is moving in a circular pattern around the earth Retrograde motion the planets seem to be moving backwards this is the problem with the geocentric system model Epicycles in the Ptolemaic theory of the solar system a circle that is followed by a planet the circle itself being centered on a larger circle within which is the Earth The epicycle accounts for irregularities of planetary motion in geocentric astronomy 2 facts that dominated at this time 0 Man and earth are the center of everything 0 Circle is the most perfect figure or shape Needed solutions Claudius Piolemy wrote quotAlmagestquot which was the first complete book on astronomy He used epicycles to explain retrograde Nicolaus Cope 39 39 s polish said sun was at the center 39chho Brahe wealthy Danish nobleman who wore a solid metal nose because he didn t have one Had a pet elk that died from falling down the stairs because it was drunk Tycho died from an exploding bladder johannes Kepler poor man extremely smart He worked for Tycho for the last ten months of Tycho s life Got all of Tycho s work and studied it He was a hard worker and the exact opposite of Tycho Kepler s 15t Law all planets orbit the sun in ellipses with the sun at one focus Planet orbits this line That circle is an ell39 se with two a Kepler s 239 1 law the line tha 39oining the sun an equal time intervals e planets sweep through equal areas in This could only happen if orbirtal pattern changes speed as they orbits Perihelion Aphelion Farthest from the Sun the point in the orbit of a planet or other astronomical body at closest to the Sun The planet is fastest as it approaches the perihelion Kepler s 3rd Law The square of the period of Revolution is proportional to the sube to the semimajor axis of the eclipse P squared a cubed Where Pyears A astronomical units This rule can be used to determine the distance to any planet in terms of AU These laws were a milestone the first time a mathematical equation was used to describe the motions of the planets Kepler had NO idea who these all worked even though they did Galileo Galilee Galileo didn t invent the telescope that was Iohanes Lippershey but he used it to study the sky Used it to discover 0 Mountains on the moon Sun spots Rotation of sun using those spots Satellites of Jupiter Rings of Saturn First observed the phases ofVenus o Figured out the Milky Way was stars not clouds Got into trouble with the Catholics because he said sun and moon were not perfect Kepler wrote Galileo for a telescope and he said no 00000 Issac Newton greatest scientist ever one inventor of calculus did work in optics and gravity Made 3 laws but was NOT the first to use Inertia that was Galileo GG is really responsible for Newton s first law Newton s rst Law aka law ofinertl39a body continues at rest or in motion in a straight line unless a force is applied Friction is a force that causes the motion of an object to change There must be force ifit s not going straight Gravity is responsible ball is being pulled by a string if that string breaksthe ball keeps ying in a line Newton realized ifyou could shoot a canon into space it would keep orbiting Newton 5 239 1 Law aka the de nition afforce Speed the distance covered divided by the time it took to cover that distance Velocity made up of two parts speed and direction ofmotion Acceleration change in velocity if neither the speed or direction changes the acceleration is zero because the velocity is staying the same 0 There is acceleration if one or both changes Force applied to a body produces acceleration The acceleration is the same as the applied force 0 Force mass X acceleration o FMA Newton 5 3 law for every applied force there is an equal but oppositely directed reaction force Universal law ofgravity every mass exerts a force of attraction on every other mass The strength of the force is directly proportional to the product of the masses divided by the square of their separation Mm r2 EqG G is the constant called the universal gravitational constant As the R gets larger the gravitational force decreases as r2 Gravitational force increases if either M or In increases while keeping a fixed distanceseparation Force is extended forever it gets weak Between earth and moon the earth is pulled toward the moon and vice versa Fma earth has a bigger mass so the moon orbits it Orbital motion planets have cen tripetalforce 2 v FC m 3 Rthe radius of the circular orbit V the orbital velocity M the mass ofthe object objects attract each other amp there is always 2 forces Surface gravity the acceleration that an object would feel near the surface ofa body The universal law of gravity tells us what the force is between 2 bodies of mass M and m 2 101 law told us what force was equal to Weight is actually a force mass is always the same 150 lbs on earth 259 lbs on moon Escape velocity speed needed to completely escape from the gravitational pull ofa body 26M Vesc r esc gt speed of light means light can t escape black hole Light and atoms We need to study the various types of radiation coming from et s and inaccessible objects Electromagnetic radiation light It s one form of radiant energy 1 Doesn t need a medium to travel 2 Fastest thing in the universe Light could travel around the earth in 13 seconds Around the moon in 128 seconds wavelength Xfrequency speed of light 1 Luminosity brightness and distance the inverse square law Luminosity the amount of energy that a body radiates each second does not depend on distance Brightness amount of energy the observer receives Difference between the two Luminosity ofa fixed source is constant but the brightness changes depending on the distance between the source and point of observance What s the relationship between brightness luminosity and distance Brightness depends on both luminosity and distance More luminous more bright Parallax used to find brightness Brightness is the amount oflight that I would see The luminosity is the brightness that doesn t change with distance They are directly proportional Brightness and distance squared are inversely proportional IfI change one of the quantities how will the others be affected Need to know 1L 4H d2 How can you calculate the difference between two unknown bulbs Ifyou have a 200W bulb and a 100W bulb the photometer would need to be closer to the 100W bulb to make the sides have equal brightness The 200W is brighter by a factor of 2 so L100W 3100 w lt d 100W 2 L200w Bzoow lt d200w2 Know how to solve for diff terms in the brightness equation and how to use the equation when you are comparing two different light sources 2 Stars Light and Spectra Example of important information or properties which can be found using a spectrum In order of decreasing wavelength radio waves microwaves infrared light Visible light ultraviolent light Xrays gamma rays What are the three basic types of spectra Describe each type and provide an example Continuous spectra the intensity changes smoothly with wavelength and all colors are presentVery hot solids liquids and some dense opaque gases emit continuous spectra Example Halogen lamp aka incandescent rainbow of all colors Emission the light is emitted at only a few particular wavelengths producing bright lines while most of the other wavelengths remain dark hot gases aurora and interstellar gas clouds are examples of objects that emit emission spectra Example Florescent lighting aka overhead lighting green and red Absorption nearly all colors ae present but light is either absent or considerably dimmer at some wavelengths producing dark lines This is produced when light from a hot dense body a continuous spectrum passes through cooler gas Absorption spectra are therefore a special case of continuous spectra with some light missing How do filters work What do the filters used in the lab represent in astronomy Filters are used to allow specific light through and blocks others Four filters red green blue and an enhancing filer made from neodymium glass it enhances reds and oranges in color photographythese will have a faint bluish color You estimate the brightness by looking through a spectrometer the color is NOT estimated by the width of the color band that is NOT the brightness Red allows lots of orange yellow Red is brightlittle green blue violet Green allows lots of green Yellow and blue are brightlittle blue barely any red orange or violet Blue allows lots of green and blue Violet is brightlittle red orange yellow The enhancing filter is VERY bright in all colors except yellow These filters represent the Earth s atmosphere and how it blocks high frequency light The upper atmosphere blocks almost all light with a WV shorter than Ultra Violet 300nm The atmosphere is almost totally transparent to visible light What will you see if you combine filters together Each filter absorbs a certain portion What is the range of electromagnetic radiation that the human eye can detect 400nm to 700nm referred to as the visible spectrum What is the rel bt wavelength and frequency How does the energy of a photon relate to the wavelength and frequency Be able to describe what is happening at the atomic level to create an emission spectrum or an absorption spectrum The absorption process is exactly the opposite of the emission process ie the bright lines in an emission spectra are the dark lines in an absorption spectra Know what type of spectrum comes from an object made up of many elements Be familiar with a solar spectrum Know how to solve for different terms in the brightness equation and how to use the equation when you are comparing two different light sources Also know how to compare brightness of the same source when you are at different distances from the source Do the math by yourself to be confident with solving this equation and using the calculator properly 3 Starry Night Introduction 39 394 are vxsxble every mght ofthe year Huw due o Draco Ceptus Cassiopeia Ursa De ne zenith pomt dmectly above the observe Huw dues yuur lucatiun an earth affea yuur zenith7 1 changes every tune you move around y me or Camelopardahs rs head nurthetn hemisphere cunstellatiunsslzrs move acrossthe sky eastemrmost locanon 4 Constellanohs Asterlsms Know howto nd and draw the followmg 51g DipperKUrsa Major Dubhe Merak Muar and Alcor thtle DipperKUrsa Mmor Polans Ursaanr Pmans Mzar 5 Am r Dunne Merak Ursa Mam Cassiopeia Schedxr 7 mm b Cass zneia Bootes Arcturus Acrumsplt am V Cygnus Deneb 7 Vega Aquila Altair Summertnangle page 250 EqL Aquila IAltar Y I Dethlnus A 7 7W I V995 7 quot quotDeneb Composed of 9 39 Cyggus Cepheus What is the definition of a sidereal day Why is it different than a solar day Why did we need to go to the dark site to observe the night sky Chapter 4 Egm is radiant energy different from sound which needs a medium speed oflight in empty space is quotcquot slows down through glass water gas colors travel at different speeds Nature oflight one theory says light is a miX of electric and magnetic energy electromagnetic wave or electromagnetic radiation It can travel because ofthe interrelatedness of electricity and magnetism Examples are starting a car and starting a lawnmower this interrelatedness is what allows light to travel through empty space small disturbance in one area causes a new disturbance in the adjacent space Photons light can be thought of a stream of particles called photons packets of energy that produce the sensation of light when entering our eyes Waveparticle duality light has 2 important properties 1 Brightness intensity is the total amount of energy carried by the light the height ofthe wave 2 Color Light and color visible spectrum roy g biv color oflight is determined by the wavelength spacing between the crests instead of describing a color we specify a quantity which is the WL WL lambda K WL are very small measured in nanometers billionth of a meter 700400 NM Red700 yellow5 80 blue480 violet400 WL is independent ofintensity Strength of radiation does not change color Freguencv ofwave crests that passes a specific point in one second hertz or Hw nu V WL and frequency speed oflight White light sun light bulbs prism spreads out white light white light is a miX of colors Electromagnetic Spectrum radio waves Xrays shorter than visible light etc that differ from light only in their wavelengths Examples radio WL 100500 meters ultraviolet light 10400 nanometers Infrared Radiation invisible but related to visible light only different from visible because ofWL some animals like snakes have sensors tht let them see in the dark Ultraviolet Light discovered 1801 by I Ritter difference in WL from light Radio Waves Maxwell first studied this then Hertz then Iansky discovered naturally occurring radio waves coming from the center of Milky Way much longer waves then visible light help astronomers view exploding stars galaxies WL decrease energy it carries increases Short WL photons carry more energy than long waves Nature of matter and heat Leucippus and Democritus called particles atoms nucleus with orbiting electrons electrons are negative nucleus is positive molecules formed when atoms link together Kelvin Temp and Radiation as an object s temp increase the object radiates light more strongly than shorter WL will heat up from red to yellow to blue Wein s law states that the WL aka the color that is radiated is inversely proportional to the temp Higher WL lower Kelvins Hotter bodies carry more energy Blackbodies absorb all radiation falling upon it excellent absorbers and emitters Individual atoms incandescent lightbulbs emit light by heating a filament to a high temp stove yellow part is the blackbody blue part is not Color of the ame depends on what is being burned Chemical Elements ex iron and hydrogen have same electrical charge throughout the atom nucleus is made ofprotons positive and neutronsno charge protons attract the equal number of oppositely charged electrons until it s neutral in charge most elements have isotopes same chemical properties with diff masses Electron orbits orbits are quantized meaning there are only a certain sizes available electrons act as particles and waves quotorbitals because they can move within their orbit circle electron movements cause a change in energy moving closer to nucleus makes atom give off energy number ofprotons in the nucleus determine what the atom is Generation oflight if the atom s energy is increased the electron moves outward quotexcited state moves inward a decrease in energy C0nservati0n ofenergy says energy is never created or destroyed it is changed in form energy lost from inward movement then energy must be shown somewhere else quotemissionquot energy released when an electron moves from a higher orbit to lower orbit ab50rpti0n reverse process energy is stored and a photon is emitted Spectrum in Spectroscopy the light emitted or re ected by the object is collected with a telescope and spread into its component colors to form a spectrum how far the electrons jump determines the color emitted Identifying atoms by their light continuous spectrum rainbow atoms packed so tight that they absorb surrounding Hot dense solids emission dark with bright lines Hot gases absorption bright with dark lines Hot through cold Astronomical spectrum strongness or weakness of a line tells the number of atoms being absorbed or emitted Doppler Shift moving light sources have diff WL toward us WL of light will be shorter away Longer Atmospheric Absorption ozone and ordinary oxygen absorb radiation oxygen and nitrogen absorb atmospheric window is when WL pass through easily this allows us to study stars amp galaxies light can be described in two ways as a stream of particles called photons or as electromagnetic waves Energy increases as WL decreases WL determines color Red light has longer WL than blue light A wave of electromagnetic energy moves through empty space at the speed oflight 2997925 km second Red light has a longer WL than blue light Chapter 6 Earth at the equator the earth moves 1000 miles an hour made of rocks oxygen silicon aluminum magnesium and iron most of the interior is mineral olivine density 55 gmcm cubed which is approx twice the density of ordinary rock iron core must rely on seismic waves speed ofwaves depends on the material through which they move Waves Pprimary waves Ssecondary waves P waves form as matter and push against other matter compressing it Travel easily through solid and liquid S waves forms as matter jerks up and down or side to side Travel only through solids Composition 4 regions Crust 20 to 70 km 1243 miles made of rocks that are silicates Mantle3500 km 2170 miles silicates specifically mineral olivine goes from crust to center Liquid or outer core 1200 km 750 miles probably made of mineral iron nickel sulfer Solid or inner core iron and nickel D139 erentiati0n occurs when a mixture of high and low density materials melt denser ones sink and lighter rise Means earth must have been almost entirely melted at sometime in the past core is HOT because the atoms are so close together that the neighbors hold and keep the substance solid Tem about 6500 K hotter than the sun s surface Age oldest rock samples on earth are over 4 billion years old solar system is probably about 46 billion years old Convection in the Earth s atmosphere occurs because heated matter expands and becomes slightly less dense than the material around it causes earthquakes volcanoes and is extremely slow Plate tectonic process of stretching and moving the crust resulting from the hot liquid dragging the surface layers in some places the process causes rifting when the surface of the crust breaks apart and molten rock rises where cool material sinks it may drag crust together forming mountains if one piece slips under another it is called subduction these two processes are the dominant forces that sculpt our landscape cause earthquakes friction stops two plates from sliding up by each other causing them to stick pressure builds rock breaks causing a sudden lurch continental drift now called plate tectonics shifting oflarge blocks of earth Pangaeasuper continent took 250 million years for the earth to look like it currently does Earth s Magnetic Field magnetic field magnetic forces stay in the field polarity important property that gives field lines a direction always start at a N pole and end at S N and S poles attract magnetic fields are generated by electric currents owing in the molten core process of rotational motion and convention called magnetic dynamo causes currents magnetic field of Earth protects us from cosmic rays Fields de ect rays into a spiraling motion around the field lines Van Allen radiation belts two donut shaped regions of trapped particles that are dangerous to space travelers aurora caused by circulating particles along the field lines they collide and move energy orbits our atmosphere protects us by blocking certain electromagnetic radiation Atmosphere surround earth there is a veil of gases atmosphere is hundreds of km like a stack ofpillows the lowest is compressed and the higher you get up there is less oxygen because it s less dense harder to breathe if you climb a mountain troposphere is about 12 km this is where the planes y and clouds are stratosphere contains the ozone layer earth is 78 nitrogen 21 oxygen the rest is Argon h20 and c02 Mars and Venus mostly c02 Jupiter and Saturn mostly H and He water vapor plays an essential role in our atmosphere specifically the troposphere because it circulates from liquid to gas and washes away the c02 in our atmosphere Greenhouse Effect water vapor traps heat hense why the temp drops drastically at night in the desert water and c02 don t make their own heat they store it and slow down the loss ofheat like a blanket greenhouse gases block infrared radiation from the earth on its way out of the atmosphere Ozone layer 03 blocks ultraviolet light that would give us a sun burn Origin of the atmosphere numerous theories 1 comet impactgases brought here from comets they were frozen water and gas which vaporized and melted 2 volcanic exhalation sunlight burned H atoms to leave N and C amp volcanic eruptions give offnecessary chemicals amp tests confirm that the gases of our atmosphere might have been released by heating the material from which our planet was formed scientists remain split on which theory is correct plants have created most of our oxygen by photosynthesis some from water molecules Coriolis Effect alters an objects path over a rotating body de ects all objects left est jetstream patterns narrow bands of rapid highaltitude winds Precession similar to the wobbling ofa spinning top as it falls over equator bulges slightly so the sun and moon exhort an unbalances attraction north star will eventually be Vega Chapter 7 Moon dark areas are smooth light areas are filled with craters large smooth dark areas are called maria basalt dark congealed lava rich in iron magnesium titanium silicates bright areas are called highlands anorthosire which is a rock type rich in calcium and aluminum silicares general less dense These two are different because they are composed of diff rock types rays radiate out ofpulverized rock perilles lunar canyons Origin of Lunar Surface Features all made from impact of solid bodies who explode on impact and turn into vaporized rock and fragments moon was molten dense stuff sank and less dense rose and set into the crust Structure moon is smaller and colder surface layer regolith meaning blanket of rocktens of meters deep Rock chunks and fine powders Usually the same material as the surface already is below this is the crust which is very thin and is thinner by earth gravity moved the core Made of silicate rock like Earth core contains little iron Absence of the Lunar Atmosphere no lunar clouds not hidden by gases making temps sore during the day and plummet at night no wind no volcanic activityno atmosphere small mass of the moon didn t keep erupted gas moon has been unchanged for millions ofyears Orbit lliptical 273 days same side always faces the earth exactly equal rotation and orbit synchronous rotation rotation is tilted 5 degrees mass is 181 of earths Origin 3 hypotheses 1 it was small planet orbiting the sun and got caught in earth s gravitational pull 2 twin formation theory 3 fission theory Now moon formed from material that was thrown from the earth when it was impacted eXplains oddities of the moonwhy there is little water stray fragments then pelted the moon created holes which then became maria Astronomy 263 exam 2 Fall 2010 CHAPTER 4 1 Light is called electromagnetic radiation because It is a mix of electric and magnetic energy 2 What is a photon How fast can they travel A photon is a stream ofparticles they are packets of energy and when they enter your eye they produce the sensation of light They travel at the speed of light 3 Color and wavelength are related because color is determined by the light s WL which is the space between wave crests For example the WL of deep red light is 7x10 7 3b Temp and wavelength are related Because shorter WL carry more energy More energy comes from shorts WL A body s temp is directly related to its energy content and the speed ofits molecular motion 4 What is the electromagnetic spectrum Spectrum of WLs The longest waves are thousands of km long The shortest are 10 18 meters or less 5 Regions of the electromagnetic spectrum from short to long WL s Gamma rays Xrays Ultraviolet Visible infrared heat microwaves cell phones TV and radio 6 Dense materials are what color 6b How does this relate to the idea of black bodies A blackbody absorbs all the radiation that falls upon it and re ects no light This is an exception to Wein s law 7 What makes elements different from eo Their composition and WLs 7b What is the arrangement in the parts of atoms There is a nucleus made of protons positive and neutrons neutral and it is orbited by electrons Chemical properties are determined by the number of electrons orbiting while the identity is determined by the number ofprotons in the nucleus 8 What s the difference between emission and absorption in terms of what happens to an electron in an atom llot dense objects produce a continuous spectrum Atoms in a gas cloud only absorb certain parts leaving lost light and this shows up as dark lines where the WL was absorbed in an absorption spectra 9 Explain how the Doppler shift affects waves re ected by or emitted from a moving body The Doppler shift is the change in WL caused by an object moving towards or away from us It helps to determine the speed and direction ofmotions ofastronomical objects The effect occurs because the WL we observe is the original WL plus the distance the source travels during the single transmission of that wave 10 What can astronomers learn from spectra s Astronomy 263 exam 2 Fall 2010 Chemical composition 11 Which gases absorb infrared radiation c02 h2 0 11b Which absorb ultraviolet 02 03 Weins law as an object heats up the WL decrease Sun is actually the hottest and emits a bluegreen color but our eye sees white Hot stars look white with a blue tint and cooler starts look white with a red tint CHAPTER 6 1 Why is the Earth not perfectly round The Earth bulges at the equator because the Earth spins fastest there The bulge is called the oblate spheroid It s also a result of inertia as described in Newton s laws of motion Gravity is a great leveler to a point The force of gravity crushed and deformed rock pulling high points down and rounding large bodies off 2 What are the most common elements composing the Earth It s mostly oxygen 46 then silicon aluminum iron magnesium and then very small parts of other chemicals It is made of rock but rockis made of chemicals The interior is mostly composed of mineral olivine 3 How do we know the Earth has a liquid core Why is the inner core solid even though it s hotter than the outer liquid core We can see inside the Earth by looking at the seismic waves caused by earthquakes Pprimary waves Ssecondary waves P waves form as matter and push against other matter compressing it Travel easily through solid and liquid S waves forms as matter jerks up and down or side to side Travel only through solids Therefore ifa lab on the far side of the earth from where an earthquake actually happened records P waves and no S waves the waves encountered liquids because they blocked the S waves The inner core is much more compressed and under greater pressure It s so hot the atoms move so quickly the bonds between them break and there is nothing to hold them together BUT since the inner core is so highly compressed the atoms are SO close the bonds to neighbors hold and keep it solid 4 What are 2 explanations that scientists offer for why the interior of the Earth is hot How hot is it First one says the E was born hot This theory says the E formed from many small bodies coming together by gravity and the impacts generated heat The surface then cooled and interior stayed hot Second says even if the E was cool at birth it got hot by things happening in nature All the rock it is made of generates radioactive electrons lk uranium This causes radioactive decay and this releases a lot of energyagain generating heat The heat is trapped under the surface 65 00 K which is hotter than the sun 5 How can Earth s age be determined By looking at rock samples and how much they have experienced radioactive decay Astronomy 263 exam 2 Fall 2010 6 What is convection Examples besides hot soup Convention occurs be heated material expands and becomes slightly less dense rises cools then sinks again 7 What s the relation between rising and sinking materials in the Earth s interior and subduction and rifting Rifting is when the surface of the crust breaks apart and molten rock rises It then cools and sinks again to be heated over and over like convection When one piece of crust slips under another it is called subduction Subduction forms mountain ranges These two processes are the dominant forces that sculpt our landscape They also cause earthquakes friction stops two plates from sliding up by each other causing them to stick pressure builds rock breaks causing a sudden lurch 8 What plate are we located Where are we going North American plate 9 What is happening where one tectonic plate is smashing into another earthquake 10 What factors are thought to be responsible for the Earth s magnetic field The magnetic field is generated by the electric currents owing in its molten core A process called magnetic dynamo combo of rotational motion and convection could have formed the field 11 How is the aurora related to the Earth s magnetic field The currents circulate around the poles driven by the magnetic lines The electrons are constantly spiraling around the lines colliding with oxygen and nitrogen The collisions excite the gases changing their energy orbits As they cool they emit light aka aurora 12 How does the fact that the Earth has a magnetic field help provide evidence for the theory of plate tectonics The molten rock formed to the Earth s magnetic field Earth s magnetic field was sometimes opposite the lava ow New crust is created at each ridge and spreads away like paper peeling off a roll and the cooling off molten rock aligns with the magnetic field at that time 13 What were the main components of the atmosphere when the earth formed And today How and why did they change Anciently it contained far more methane and ammonia than it does now both are poisonous Today it is mostly nitrogenamp oxygen and a tiny bit of argon and water The sunlight probably burned off the hydrogen out ofboth of these atoms and left N and C 14 Explain the Greenhouse effect and how it relates to global warming The Greenhouse effect he the atmosphere is not transparent to the infrared waves that are created by the sun hitting the surface absorbed and then converted to heat which is trapped If the Earth begins to trap too much heat because humans are produced too much c02 the temp will rise 15 What is the ozone Why is it important o3 The ozone layer is formed be at these upper levels solar ultraviolet radiation splits 02 bonds and these split bonds connect to actual 02 atoms to form 03 Without the ozone layer the ultraviolet light would seep to the lower layers and we would get severe sunburn by just walking outside 16 What is the Coriolis Effect How does it affect life on earth The Effect alters the path ofa moving object over a rotating body like the earth or stars Example You re standing at the North Pole and throw a rock to the equator the earth will still spin underneath you Astronomy 263 exam 2 Fall 2010 so the rock arches and makes it hit to the right It affects the weather ocean currents creates trade winds It also establishes the jet stream 17 What is precession The wobbling that occurs as a top spins and begins to fall over slowly If Earth were perfectly spherical then precession would not occur 18 What are some of the possible consequences Polaris will not be our north star for ever it could also cause climate changes CHAPTER 7 1 How is a crater formed and what is it Why do some have maria 2 How do maria differ from highlands How were the formed Why are they smooth Maria are made ofa lava called basalt which is a dark congealed lava rich in iron magnesium titanium silicates N 0 water Highlands are bright areas surrounding the maria They are different from maria because they are made of different rock types Highlands are made of anorthosite which is a rock rich in calcium and aluminum It s less dense then maria and considerably older More rugged 3 What are lunar rilles What are rays Lunar rilles are lunar canyons maybe carved out by ancient lava ows wind away from some craters Many craters have long light streaks of pulverized rock called rays that radiate outwards 4 List the structure and composition of the Moon from surface to core How is it diff from earth Surface layer regolith meaning blanket of rocktens ofmeters deep Rock chunks and fine powders Usually the same material as the surface already is Below this is the crust which is very thin and is thinner by earth gravity moved the core and is made of silicate rock like Earth The mantle is rich in olivine the same type of dense greenish rock that composes most ofthe Earth s mantle It s cold and rigid though and can t be heated like on earth The core contains little iron It can t generate a big gravitational pull The moon cooled and cools much faster than the earth The moon is also smaller than the earth so there is much less radioactivity to create heat 5 Why does the moon lack an atmosphere There are no lunar clouds it s not hidden by gases making temps sore during the day and plummet at night There is no wind There is no volcanic activityno atmosphere The small mass of the moon didn t keep erupted gas and the moon has been unchanged for millions ofyears 6 What are two ways to determine the distance to the moon Triangulation radar or laser beam or to bounce a radar beam off of special re ectors that were places on the moon by people oprollo 7 How do astronomers think the moon was formed What supports this theory How much does this theory explain why the Earth and Moon have such diff densities Originally 3 hypotheses Astronomy 263 exam 2 Fall 2010 1 It was small planet orbiting the sun and got caught in earth s gravitational pull 2 Twin formation theory 3 Fission theory Now the moon formed from material that was thrown from the earth when it was impacted This explains oddities of the moonwhy there is little water It explains moon s composition because only our crust was blown off leaving the iron core Stray fragments then pelted the moon created holes which then became maria so the moon is made of earth and other fragments 8 Why is the moon cratered and the earth is not The earth melted more materials together and continued to as the moon stopped 9 How are the tides formed on earth The earth exerts a gravitational pull so does the moon creating the differential gravitational force 10 Why does the moon form two tidal bulges on the earth Gravity pulls the oceans into a tidal bulge on the side of the earth facing the moon The one of the far side is a result of the moon s gravity pulling the earth out from under the water 11 How are the tides formed on earth The earth s spin carries us from one bulge to another There are two high tides each day Ifyou imagine a person standing on top of the earth like at the north pole and the moon is to the rightthere would be a low tide As the earth spins and puts a person on the left side of the earth with the moon still to the right there is a high tide because it s always pulling sideways 12 How does the moon rotate Why does it spin like this CHAPTER 8 1 Name the eight planets in order of increasing distance from the Sun MVEMSUN Mercury Venus Earth Mars Iupiter Saturn Uranus Neptune 2 Sketch the solar system 3 Make a table of the inner and outer planets InnerMVEM Outer ISUN 4 What properties distinguish the planets Inner are small rocky bodies with relatively thin or no atmosphere Called terrestrial Outer are gaseous and liquid much larger and have deep hydrogenrich atmospheres Called Iovian 5 What is the Oort cloud Where is it located and what of objects come from it Oort s cloud is named after a Dutch astronomer who said this is a region that completely surrounds the Solar System and extends from about 40000 to 100000 AU from the sun Most comets come from here Contains over 1 trillion comet nuclei larger objects and dwarfplanets including Pluto 6 How do we know the composition of Jupiter From density comparison and space probes 7 What is Bode s rule Astronomy 263 exam 2 Fall 2010 Each planet is about twice as far from the Sun as its inner neighbor This relationship can be expressed by a simple mathematical relations know as Bode s rule Write down 03 and keep doubling the number until you have 9 numbers Then at four to each and divide by 10 These numbers are very close to the actual distance in AU 8 What is an interstellar cloud What does it have to do with the Solar system An enormous rotating aggregate of gas and dust They are common between the star and galaxies of today This cloud is the raw material of the whole Solar system The clouds formed into planets and the sun when the gravity pulled the particles in The cloud then attened 9 What is the solar nebula What is its shape and why The cloud then became a rotating disk with a bulge at the center known as the solar nebula The bulge became the sun 10 Why are there two main types of planets The sun heated the inner parts of the disk but the sun couldn t heat past the orbit oqupiter The inner planets never dropped enough in temp to condense the water and other chemicals like water but it did condense iron and silicate 11 What is the difference between condensation and accretion Condensation is the change from gas to liquid or when a gas cools and it s molecules still together to form liquid or solid particles Accretion is when the tiny particles that condensed from the nebula begin to stick together to make bigger pieces 12 What are planetesimals Small planetlike bodies 13 What is the planetesimal theory of creation Planets near the sun formed from silicate and iron while the outer ones incorporated ice and frozen gas Inner become rockyiron ones and the outer become icyrockyiron ones 14 How does this explain the asteroids 15 How did the craters we see on many planets form 16 Describe the theory on how planets formed their atmospheres 17 18 What observations of other solar systems have been made that support the solar nebula hypothesis 19 What are two methods used to find exoplanets 20 How do some exoplanets differ from what we might expect Does this prove the nebula theory is wrong