Introduction to the Sky and Solar System
Introduction to the Sky and Solar System ASTR 1210
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FINAL EXAM STUDY GUIDE according to the concept list CHAPTER 1 Universe is ever expanding Explaining into nothingdoesn39t exist 186000 miles per seconds in space speed of light light year 186000 miles per sec in a year Earth is traveling 12 million mph around center of galaxy AU distance from Earth to the Sun 149598000 kilometers Parallax way to measure distance thumb in front of eyes and switch from right to left eye CHAPTER 2 Star patterns Constellations The constellations are totally imaginary things that poets farmers and astronomers have made up over the past 6000 years and probably even more The real purpose for the constellations is to help us tell which stars are which nothing more The constellations help by breaking up the sky into more managable bits Asterisms different names given to constellations veiwable from the northern hemisphere EX the big and little dipper are asterisms for ursa minor and ursa major o Stellar brightness magnitude the brighter the star the smaller the magnitude values The brightness of a star is diminished by distance Hipparchus backward exponentaial Hipparchus ranked stars in six magnitude classes according to their brightness he assigned the value of one to the twenty brightest stars to weaker ones a value of two and so forth to the stars with a class of six which can be barely seen with the naked eye A similar system is still used today 0 Celesital sphere celestial sphere imaginary sphere of infinite radius with the earth at its center It is used for describing the positions and motions of stars and other objects For these purposes any astronomical object can be thought of as being located at the point where the line of sight from the earth through the object intersects the surface of the celestial sphere celestial sphere stars are randomly scattered throughout the sky the sky has no depth the theoretical globe that encompasses the sky celestial poles the two imaginary points in the sky where the Earth s axis of rotation quotin nitely extendedquot zenith the highest point a celestial body reaches while in orbit Equator o Called so bc it s equal distance from the north pole as it is to the south pole Celestial sphere ie the sky 0 Celestial horizon we see it as though the world is at and its extended throughout the horizon Your horizontal lines from where you are to the celestial sphere Book de nition is a great circle parallel to the horizon the center of which is the center of the Earth o Celestial equator the equidistance down from the two celestial poles Every one no matter where they are on the Earth are in the same celestial sphere have the same celestial poles and the same celestial equator o The things that aren39t shared among everyone on the planet but depends on your position are Zenith the top end of your vertical line line from where you are vertically straight to the celestial sphere Nadir the bottom end of your vertical line Is it possible for two people to have the same zenith Yes only if you re in a special relationship with each other Actual horizon a boundary that divides what we can see from what we cannot see 0 Rotation the spinning of an object around its axis 0 Earth rotates once each day on its axis imaginary line connecting North Pole to South Pole through center of earth 0 Earth rotates from west to east Orbit revolution the orbital motion of one object around another 0 Earth orbits around the Sun once each year o Ecliptic plane at plane de ning Earth s orbital path 0 Ecliptic the path the sun follows as it appears to circle around the celestial sphere once each year 0 Sun crosses celestial sphere at 235 degree angle because that is the tilt of Earth s axis Inclinati0n axial tilt Earth is on a 235 degree inclination Axial tilt is the inclination angle of a planet s rotational axis in relation to its orbital plane Seasons These 4 events start the seasons Vernal equinox 7 when the sun crosses the celestial equator going northward Spring Summer solstice 7 the sun is at its most northern point Summer Autumnal equinox 7 the sun crosses the celestial equator going southward Winter solstice the sun reaches its most southern point Solstices 7 When the sun comes to rest and begins to stop rising and start falling or vice versa Summer solstice longest day and shortest night Winter solstice longest night and shortest day Equinoxes 7 Day and night are about equal Perihelion 7 Earth s closest point to the sun January 4th Aphelion 7 Earth s most distant point from the sun July 4th Southern Hemisphere Half of planet south of the equator Seasons are softer than those in the northern hemisphere because there is vastly more water in the southern hemisphere which helps to moderate the temperature Magellenic Clouds found here Northern Hemisphere Half of plant north of the equator Half of celestial sphere north of the celestial equator Contains most land and most of population Seasons are more extreme Planetary Motion Mercury and Venus are referred to as Morning and Evening stars because they can only be seen soon after the sun sets or before it rises This is due to their proximity to the sun Planets are wandering stars Zodiac Region surrounding the ecliptic by 90 on either side that is divided into twelve equal stations measuring 30 Astrology The study of the position of the stars with the belief that this has a direct impact on the Earth and human action Phases of the moon new crescent quarter gibbus full New Moon Waxing Crescent First Quarter Waxing Gibbous Full Moon Waning Gibbous Last Quarter Waning Crescent New Moon EXplanation Half of the moon is always in sunlight We always see one face of the moon so the phases come from the portion of this face that is lit Syn0dic period 295d Time to get from one full moon phase to another full moon phase to get back in line with the EarthSun line Sidereal period 273d Time it takes it to go 360 degrees around the Earth Axial rotation period 273d the Moon orbits Earth once every 273 days synchronous motion the Moon rotates once on its aXis in the same time that it makes a single orbit of Earth ecipses Lunar eclipse occurs when the Earth lies between the Sun and the Moon so the Earth39s shadow is falling on the moon Solar eclipse occurs when the Moon lies directly between the Sun and the Earth so the Moon39s shadow falls on the Earth so the Sun is fully or partially blocked from view umbra penumbra Shadow of the Moon or Earth has two parts Umbra where sunlight is completely blocked Penumbra where sunlight is only partially blocked Ancient Greek Astronomers Aristotle prominent Greek philosopher and scientist Believed that only four elements existed in the universe and everything in existence was made from them earth air water and re Earthly and watery things move toward the center of the universe which was the earth geocentric so the earth must be round because water and earth move toward the center from all directions 0 Proof the earth was round round shadow can t be cast by a nonround object Fiery and airy move away from the center to form the atmosphere sun stars etc The nature of earthly things was to be at rest and because the earth is an earthly object for it to move something must push it so the earth is stationary A crystalline sphere surrounds the earth and keeps in the air and the moon sits on this sphere The sphere rotates so the moon moves The sun and all of the planets have their own spheres each moving at different speeds The crystalline spheres are circular because circles are quotperfectquot and the motions of the heavens must be perfect However there were two issues with this model that were resolved rather badly o l Epicycles circles on top of circles were needed for the observed orbits of the planets to line up with the predicted orbits o 2 Equant because the sun moves slower at certain times of the year a point slightly off center from the earth was chosen for the sun to revolve around known as the equant ParallaX using two measurements to determine the motion or distance from another object like how we use two eyes to perceive depth Observe an object ie planet one day then a week later observe again and based on the time between the viewings and the distance the object moved the distance to the object can be calculated Ecipse seasons precessi0n 0f moon39s orbit ecipse predictions saros cycle Eclipse seasons the two periods each year when the nodes of the moon s orbit are nearly aligned with the Sun 0 Each eclipse season lasts a few weeks 0 Some type of lunar eclipse occurs during each eclipse season s full moon and some type of solar eclipse during its new moon Nodes slowly move around the orbit I Eclipse seasons occur slightly less than 6 months apart 0 A No Eclipse 7 BEclipsc lt7I H 39gtlt 1 UH v C No Eclipse Dh Eclipse thureIJ n L 4 1113 days 0 Befom it was used to predict eclipses Prenessinnr me wows because of spmnmg spmmng top Earth dwh erem hemwsphere Wm be Med towards the Sun at agwen pomt veer and mm A A A Wm occur durmgthe same pan ohhe veer 7 Eclipse Seasonsperiods during 6 Take clean sheet ofpaper and put d m Sun L where you can have eclipses 0 in ch middle ofit which hephesems Pim ofwhite papa would be ecliptic r hg ch circle which hephesems ch Earth m a dot on ch notecardto represen e Earh r draw a circle around the Earth to represent ch Moon s orbit r The moon s orbitis tilted up about 55 degrees what you would like to do is put the earth where it should be matched up with the other dot Fold the moon s orbit in half to represent how it would look at the 5 degree angle along the ecliptic Nodes2 points where the moon s orbit crosses through the ecliptic going down and coming up Open up your card and draw a line between the 2 nodes fold line of your card This line drawn is called the Line of Nodes Moon s orbit around the Earth acts as a gyroscope In order to have an eclipse the moon must be near a node and the sun and the moon must be lines up with each other which can only happen if the line of node is lined up with the sun Moon moving around the Earth is a rotary motion gyroscope but there is another property it percepts which cause the lines of node to gradually rotate After 185 years it will have made 1 precession Precession gradual wobble that changes the orientation of earth s aXis in space For each orbit you lose about 20 years CHAPTER 3 Aristotle prominent Greek philosopher and scientist Believed that only four elements existed in the universe and everything in existence was made from them earth air water and re Earthly and watery things move toward the center of the universe which was the earth geocentric so the earth must be round because water and earth move toward the center from all directions 0 Proof the earth was round round shadow can t be cast by a nonround object Fiery and airy move away from the center to form the atmosphere sun stars etc The nature of earthly things was to be at rest and because the earth is an earthly object for it to move something must push it so the earth is stationary A crystalline sphere surrounds the earth and keeps in the air and the moon sits on this sphere The sphere rotates so the moon moves The sun and all of the planets have their own spheres each moving at different speeds The crystalline spheres are circular because circles are quotperfectquot and the motions of the heavens must be perfect However there were two issues with this model that were resolved rather badly o l Epicycles circles on top of circles were needed for the observed orbits of the planets to line up with the predicted orbits o 2 Equant because the sun moves slower at certain times of the year a point slightly off center from the earth was chosen for the sun to revolve around known as the equant Parallax using two measurements to determine the motion or distance from another object like how we use two eyes to perceive depth Observe an object ie planet one day then a week later observe again and based on the time between the viewings and the distance the object moved the distance to the object can be calculated Show quoted text Eratosthenes estimated the radius of the earth by finding the degree of the angle of a shadow cast on the earth by the sun By using basic geometry of parallel lines determined the angle of the light from the sun on the center of the earth is the same of the angle of the shadow Check out page 68 in the book for this picture it helps to explain a lot You can then set up this equation d We 7 Y pi Y r A angle 360 degrees 360 angle in degrees Aristarchus first to suggest that the Earth goes around the sun heliocentricity Moon Earth watch the moon go into the solar eclipse If you watch the phases of the moon you can determine the size of the sun Because they appear to be the same size Aristarcus argues that the largest object should be in the center of the solar system He was the first person to logically argue this The sun is actually a lot further away from the Earth than the moon Hipparchus developed the circleuponcircle idea into a model that could predict planetary positions He included in his model smaller circles that moved on the original set of circles and these were slightly offcenter from earth He discovered precession invented the magnitude system for describing stellar brightness 1 Chapter 3 a Direct Motion i The motion of planetary bodies that is similar to the motion of other planets in the system ii East sets before the Sun West sets after Sun 1 Mars Jupiter and Saturn move toward the East relative to the stars 2 Mercury and Venus are sometimes on the East or the West b Retrograde Motion i Backwards Motion West 7 East 1 Venus travels in Retrograde 2 Uranus because titled travels in RM depending on how one looks at it c Ptolemy i Compiled all the research that greek astronomers found in Library of Alexandria ii Compilation called The Almagest iii Compilation of astrology called The Testrabiblos d Deferent the circular path a planet took around the earth e Epicyclecircular path each planet travels on while orbiting earth on a deferent f Eccentricity determines type of orbit i E 0 is a circle ii E l is a line iii E 0ltEltl is an ellipse g Equant point in space parallel Earth s point in space that sun travels around Giordano Bruno was arrested for blasphemy and heresy against the Catholic church He was sentenced to death for supporting Copernicus heliocentric model of the universe when the church supported the geocentric model He was burned at the stake Galileo came up with the idea of friction and since it is the nature ofthings to be in motion gravity pulling on two touching objects slows the one in motion down Gravity causes things to fall at the same time independent of weight and he was the first person to look at the sky with a telescope First to see the moon surface with geography and that the Sun has spots changing modern thinking that the heavens were perfect Saw that Venus has full set of phases and that there were 4 objects orbiting Jupiter He wrote quotThe Dialoguequot with a discussion of the church view Copernican view and a mediator The church forced him to recant his views excommunicated him and put him on house arrest for the rest of his life Faint stars Galileo saw stars that were invisible to the human eye Made no theological sense that man couldn t see but was a blow to the validity of theology Stars were supposed to be signs and symbols to man so if man couldn t see them he was contradicting whole theological theory surface of moon Observes with his telescope the surface of the moon and said that it had mountains and oceans maria satellites of Jupiter Galileo contradicts Ptolemaic theory with the use of his telescope discovers four objects orbiting Jupiter but everything orbits the earth so again contradicting Greek theory spots on sun Referred to by Galileo as blemishes Contradicted the theory that the heavens were perfect PHASES 0F VENUS Equam Cemev m epmyme muves mum mucmse my mum and epmyme muves cuumevc uckwwse Epmyc e mmmn s m mam umumn D even m 7 nm p anefs epmyme names m an cyc um pawpmm Hhvuugh 7 sutha The cumbmed mmmn 5 Shawn at quotgm WWW wugym taut 5523 DEfErEnt Maj or rotau on of planet Venus and Mereury are attaehedto a hne from the Earth to the Sun They are boundto the le or nght of the sun Order Earth m eenter Mereury Venus Sun others EARS 0F SATURN tu was vrsrble from vrsua1 srght however rtwas rrnpossrble to see rtweu enough to ten thatrthadnngs Gahleo could not see wrth the equrprnent avauable that Saturn had nngs rnstead he saw apau ofunexplamed ears on erther srde of Saturn DIFFICULTIES WITH CHURCH There were dA 39xculues wrth the ehureh backm the day as astronomy eon reted wrth h s EarthCentne mew ofthe world Co ernreus hadrssues wrth the Chureh pubhsh for fear ofpersucuuon by the e ureh Note Brahe dAdnothave to Worry about sueh rssues He was hrs book was put on the banned bookquot hst Tycho Brahe Saw what he called a nova we call today a quotsupemovaquot and by measuring its parallax and then comparing it to the moons parallax found that the nova was much further away He also made a similar observation with a comet and found that it too was not in the Earth s atmosphere Parallax and supernova From Earth if using a telescope and watching a certain star one should see that as the Earth moves around the sun the star should appear to move back and forth against the background of more distant stars The ancient Greeks were unable to detect stellar parallax which is why they could not accept a suncentered solar system Supemova the explosion of a distant star Observatory at Hveen Tycho Brahe s observatory given to him by his friend the prince of Denmark when he became King Doesn t have a telescope here but a quadrant Compiled nakedeye observations Loses his observatory when the King dies because the new King did not like Tycho Special Model of solar system Brahe s inability to detect stellar parallax led him to conclude that Earth must remain stationary His model therefore said that the all planets orbit the Sun and that the Sun and this system orbits the Earth Inertia the tendency of all objects to resist a change in motion and is dependent on the object s mass Kepler hired to try and prove Copernican theory correct laws explain planetary motion apply to anything that orbits 1st law Planetary orbits are elliptical with the sun at the focus asemimajor axis fcenter from distance to one focus eccentricityf a 2nd law The radius vector sweeps equal areas in equal times 3rd law cpAZ is proportional to aA3 01 pyrs aau CHAPTER 81 0 Day 0 Sidereal day the amount of time it takes for the Earth to rotate 360 degrees Can be measured by measuring how long it takes any star to go from its highest point in the sky one day to its highest point the next day about 23 hours and 56 minutes Means related to the stars measurement will be the same regardless of which star you choose 0 Solar day the typical 24hours day on our calendar It is based on the amount of time it takes for the Sun to make on circuit around the local sky A solar day is about 4 minutes longer than the sidereal day because of the simultaneous rotation of the earth on its own axis and the orbit of the earth around the sun Because the earth moves about 1 per day around in its orbit it must rotate an extra 1 equal to about 4 minutes in order for the Sun to be in the same place in the sky 0 Week ancient Greeks named the seven days of the week according to the belief that each of the planets had in uence over a designated day of the week 0 First day Sol or the Sun Second day Luna or the Moon Third day Mars Fourth day Mercury Fifth day Jupiter Sixth day Venus and the Seventh day Saturn 0 Month 0 Synodic month 295 days the period required for the moon to make one full cycle of phases Not the moon s true rotation periodiEarth s motion around the Sun means that the moon most complete more than one full orbit of Earth from one new moon the next because new moon is created by the moon s relative position to the sun and the earth 0 Sidereal month 273 days the moon s true orbital period Describes how long it takes the moon to complete an orbit relative to the positions of the distant stars 0 Year 0 Sidereal year time it takes for Earth to complete one orbit relative to the stars 0 Tropical year 20 minutes shorter than the sidereal year Based on the cycle of the seasons measured from the time from one spring equinox to the nexti precession causes the slight difference in the two measurements Every 72 years the sidereal year gets out of sync with the seasons by 1 day 0 Seven planets of the Greeks Mercury Venus Mars Jupiter Saturn the Sun and the Moon The word planet comes from the Greek word planetes which means wanderer 7 referred to the heavenly bodies that moved around the sky relative to the stars 0 Days per year 3652422 days the precise length of the year Ancient Egyptians found that their calendars were drifting out of sync with the seasons by 1 day every 4 years To resolve this problem Julius Caesar introduced the Julian calendar which made 366 days in a year every fourth year However this is not even precisely correct it is still off by about 11 minutes so the Gregorian calendar was introduced so that the leap year does not occur when the century is changing 1700 1800 1900 etc except if the year is divisible by 400 1600 2000 etc Julian Calendar1st calendar to integrate leap year system though still of by 10 days in a year 0078 minutes a day Grago ancalendar that we use now off by 2425 Problem solved by leap year Leap year each year that is divisible by 400 ex 2000 2400 Timelocalsundailtime apparent solar time time measured by the sun Meridianimaginary circle perpendicular to the celestial equator and horizon Mean Local Time Local time is UT adjusted for location around the Earth in time zones Its reference point is one s immediate locality when it is 120000 noon Paci c Time at JPL it is 200000 UTC and 130000 Mountain Time in Denver Colorado Many locations change between stande time and daylight saving time see below Local time is also determined on other planets when needed Local time on another planet is conceived as the equivalent value of time for the Sun39s distance from the meridian as it is on Earth A planet that rotates more slowly than Earth would have an object in its sky at 100 local time move to 200 local time in more than an hour of Earthclock time Around 1130 am or 1230 pm at a particular location on Venus the sun would be nearly overhead At 500 pm at a particular location on Mars the sun would be low in the west Zone time The world is divided into a number of standard time zones Roughly speaking there are 24 time zones spaced at intervals of 150 in longitude Practically due to geographic and political factors the boundaries of time zones are more circuitous In addition a few time zones are offset by an odd number of half hours from the Greenwich and U S time zones Within the confines of each time zone the hour and minute of the day is defined to be the same Time zones eliminate the problem that local noon defined according to the elevation of the Sun actually occurs at a different time for nearby towns at slightly different longitudes so that each town s clocks differ by a few minutes from those of neighboring clocks This problem was already encountered in making up timetables for long distance train travel but became completely unmanageable with the advent of modern air travel Defrning time zones means than watches need only be adjusted in one hour steps upon crossing of a time zone boundary as opposed to continuously along any eastwest journey Greenwich Universal Time Universal time UT is simply the number of hours minutes and seconds which have elapsed since midnight when the Sun is at a longitude of 180 in the Greenwich time zone Since the Earth39s rotation is irregular at the 01 second level a local approximation to universal time not corrected for polar motion is often used This is called UTO and also referred to as Greenwich mean time abbreviated GMT In UTO 24 universal hours are defined to be a mean solar day International date line An imaginary line which generally follows the 1800 meridian of longitude one half of the way around the Earth from the Greenwich prime meridian Actually for political and geographic reasons the International Date Line makes detours around the Aleutian Islands in Alaska and some of New Zealand and actually follows time zone boundaries over some latitude ranges The date line marks the boundary between calendar days so that the date on the New Zealand side is de ned to be one day after the date on the Alaska side Since the line passes down the middle of a time zone over most latitude ranges one would switch by an hour at 17350 W a day at 180 and an hour again at 17350 E The construct of a date line is necessary to prevent the continuous accumulation or loss of days as travelers move around the globe as compared to days reckoned by inhabitants remaining in a xed location The date line resolves this potential dif culty but can lead to paradoxes such as a traveler on a long trip from the Asia arriving in the United States several hours before leaving his point of departure CHAPTER 4 Newton 1St law an object at rest or in motion will remain at rest or in motion in a straight line unless acted by a new unbalanced force Inertia property in matter that allows it to resist changes in velocity speed and direction The peculiarity of mass is that its inertia is equal to its attractiveness Momentum product of mass and velocity mass times velocity momentum Can only change an object s momentum by applying force Force The only way to change an object s momentum De ned as a mass times and acceleration F ma and measured in Newtons N A vector quantity The subject of all three of Newton s laws especially the second Net force is the rate of change of momentum Velocity A vector quantity de ned by a speed and a direction The rate of change of position Velocity of an object does not change unless it is acted upon by a force Meters per second ms Acceleration A quantity that describes a change in velocity either speed or direction Meters per second squared msz Also a vector quantity If an object is accelerating any change of speed or direction of motion it must be acted upon by a force Vector and Scalar Quantities A vector quantity has both a magnitude and a direction such as velocity a scalar has only a magnitude such as speed Vector addition Vectors are typically drawn on a Cartesian coordinate system The magnitude of a vector is represented by its length and the direction is represented by its orientation To add two vectors together place the tail of one vector on the tip of the other The resultant vector tail of the rst to tip of the second is the sum of the addition Alternatively the vectors can be resolved into components usually X an y and added separately This one is kind of hard to explain without a picture so Google vector addition if you re having trouble visualizing it 2quot 1 Law Force is equal to mass X acceleration If there is a net force the object will accelerate in proportion to the net force and therefore acceleration requires force Fma Fia iinertiaconstant 3rd law For every force there is an equal and opposite reaction force NEVER ON THE SAME OBJECT Law of Gravity F Gmmdz Every mass attracts every other mass The strength of gravitational force between masses is directly proportional to the product of the masses and decreases with the square of the distance between objects G is a constant with a value of 667 X 103911 and units ofm3 kg X s2 Peculiar Properties of Mass Inertia is the tendency of an object to resist changes to its velocity The inertia of an object is directly proportional to its mass Inertia is the subject of Newton s first law It is better explained in some cases by special relativity Gravitational attraction is the subject of Newton s universal law of gravitation It states that gravity is a property inherent to all mass and directly proportional to the mass of an object It is responsible for weight tides convection and other physical phenomena Gravitation is better explained by general relativity Orbital motion Bound orbits on which an object travels repeatedly around another object 0 Bound orbits are an elliptical shape Unbound orbits on which an object comes in toward a large body only once never to return 0 Inbound orbits may be parabolic or hyperbolic in shape Open 7 meaning the object will not return Closed 7 meaning the object will return What keeps the moon quotupquot Nothing the moon is falling around the Earth in a curved path gravity is pulling in on the moon Centrifugal forces The apparent force equal and opposite to the centripetal force drawing a rotating body away from the center of rotation caused by the inertia of the body An effect that seems to cause an object moving in a curve to be pushed away from the curve s center Centrifugal force is not a true force but is actually the effect of inertia in that the moving object39s natural tendency is to move in a straight line Centripetal forces is necessary for an object to move with circular motion a force that acts inwards on any object that rotates or moves along a curved path A force acting on a moving body at an angle to the direction of motion tending to make the body follow a circular or curved path EX The force ofgravity acting on a satellite in orbit Weight the net force than an object applies to its surroundings o In the case ofa stationary body on the surface of the Earth Weight mass X acceleration of gravity Mass the measure ofthe amount of matter in an object quotWeightlessquot a Weight ofzero as occurs during freefall CON39IC SECTIONS Cut straight across gt circle Cut at an ang1e gt ellipse Cut parallel to side ofcone gt parabo1a edge ofcone gt hyperbola Parabola cutting plane parallel to side of cone Circle and Ellipse Hyperbolas NEWTON S VERSION OF KEPLER S LAWS 1 Orbits are conic sections 2 Same as Kepler s 2 Law 3 rn m2p7 is parallelto a3 gt krn m2p2 a1 A km5mmemhlightyearz Iau3 rn2 are two objects ksolar masslight year2 1an in orbit around one another and Ac ignore rnass ofeanh p is the period because it s so miniscule Could gure out how to get the mass of the sun m1 m2p2 a3 CHAPTER 7 Origin of the Solar System based on patterns and traits of planets Not a random collection of worlds Comparative planetology helps us determine the formation of the solar system The patterns and traits we observe among the planets give us hints to how our solar system was born and has evolved These main pattemstraits include Patterns of motion among large bodies The sun planets and large moons generally orbit and rotate in a very organized way nearly circular lie in nearly the same plane orbit the sun in same direction Two major types of planets rocky terrestrial planets close together and close to the sun vs the large gasrich jovian planets farther apart and farther out also made of hydrogen hilium and hydrogen compounds Asteroids and comets Locations orbits and compositions of these asteroids and comets follow a distinct pattern Exceptions Earth unique among inner planets by having a large moon Uranus has an odd sideways tilt CHAPTER 8 Modern origin theory Stellar evolution Hydrogen gas atoms that form and nearby atoms join the concentration and increase the concentration make everything hotter and causes ionization and protons collide and come together and changes from hydrogen to helium hydrogen fusion Fusion process causes some mass to become lost and that mass turns into energy energy tries to expand it and opposite force is pushing inward causing the formation of a star origin of the elements Original solar system made up of H2 and Helium but reactions between atoms due to hot temperatures within stars produced elements up to Fe before exploding explosions led to new stars and the repetition of the process solar nebula model Shows that 46 bya star formed a spinning disc that was attracted to itself gravitationally so began to compact and form a spinning disc over time As the sun began to condense spun faster which led to the shedding of its outer layers in order to form planets contraction of sun from cloud Materials are pulled towards the center due to gravity and center becomes hot enough creating an environment where atoms begin to collide and stick together with very hot center fusion in sun stops contraction rotating disk around sun Outer layers are most gaseous and travel more quickly due to Fma planetesimals form condensation Frost line before this line only heavier metals and materials able to condense which explains why there are two types of planets Condensation growth by which a particle adds matter one atom at a time from surrounding gas planetesimals coalesce accretion Smaller clusters collide and as a planetesimal forms keeps colliding with smaller clusters to grow in size Accretion sticking together of solid particles planetsmoons form At some point you begin to run out of hydrogen in the middle of the stars Hydrogen fusion eventually stops which means that energy process quits When energy process quits gravity squeezes core region down causing it to get hot If it gets hot enough can take three helium nuclei and slam them together in order to form carbon atom If you take a large concentration of gas and let it shrink in size know that gas if it has any circular motion at all the rotation will speed up as cluster is made smaller When looking at sun top and bottom are falling to the center but sides are spinning in circular motion Would expect to end up with a ball in the middle with spinning gas around the outside 1 Angular Momentum Astronomy deals more with angular momentum This is also conserved and is the mass of the object velocity of the object and the radius of the object If the radius gets bigger the velocity has to get smaller to go with the conservation idea An example of this is the speed of the ice skater s twirl The larger the twirl the slower the spin This idea can be related to the formation of the sun If you take a large cloud of gas and let is shrink inside if it has any circular motion and you make it smaller it ll speed up This is conservation of angular momentum The sun is spinning slowly The gas that was on top and below the sun will fall toward the center The gas on the sides is spinning gas and wont fall toward the center because it is spinning This is the gas at 3 o clock and 9 o clock We think the sun formed and in that process because it was spinning it left behind some of its gas in a disk around the sun If you have a spinning disk the planets will be going in that direction The disk is made up of gas which is the same gas that made up the sun It would ve been part of the sun if the sun wasn t spinning As the lines of force go through the disk material it speeds up and slows down the sun That process is called magnetic breaking This can also be put into a formula where the angular momentum mvr M is the mass of the small object v is the magnitude of its velocity and r is the separation between the objects 2 Differentiation in solar nebula The churning and mixing of gas in the solar nebula should have ensured that the nebula had the same composition throughout 98 hydrogen and helium plus 2 heavier elements The terrestrial planets and jovian planets differ because of where they formed The terrestrial planets formed in the warm inner regions of the swirling disk while the jovian planets formed in the colder outer region In the center of the collapsing solar nebula gravity drew together enough material to form the Sun In the surrounding disk the gaseous material was too spread out for gravity alone to clump it together This is the creation of planetecimals The general process in which solid particles form in a gas is called condensation Different materials condense at different temperatures Because hydrogen and helium gas made up 98 of the solar nebula s mass and did not condense the vast majority of the nebula remained gaseous at all times Comets have two visible tails one made of ionized gas or plasma and the other made of dust The plasma tail consists of gas escaping from the coma UV light from the sun ionizes the gas and the solar wind then carries this gas straight outward from the Sun This tail extends directly from the sun The dust tail is made of dustsize particles escaping from the coma These particles are not affected by solar wind and instead are pushed away from the sun by much weaker pressure of sunlight itself called radiation pressure This causes it to have a dust tail that points away from the sun and has a slight curve back in the direction that the comet came from 3 Rotation V Revolution A rotation is the planet spinning around once on its axis while a revolution is its complete path around the sun CHAPTER 9 Earth as a planet Earth has been affected by the same geological processes as other planets but erosion is far more important to our world Also our unique plate tectonics are very unique to our existence Earth s geology seems to be destined from birth by fundamental properties of size distance from the sun and rate of rotation Density of Earth is 552 gcm3 Differentiation the process in which gravity separates materials according to density with highdensity materials sinking and lowdensity materials rising Earth s interior rocky crust I represents earth s outer skinlower density mantle 7 inside surrounds core medium density metal core highest density and rigid lithosphere crust and part of mantle Pwaves type of seismic wave P stands for primary but it is easier to think of it as pushing Can travel through almost any material because molecules can always push on their neighbor These waves result from compression and stretching in the direction of travel The liquid outer core of the earth bends P waves Swaves other type of seismic wave S stands for secondary but it is easier to think of it as side to side These waves only travel in solids because liquids and gasses have bonds that are too weak to transmit up and down or sideways forces These waves vibrate up and down or side to side perpendicular to the direction of travel The liquid outer core stops S wave innerouter core core the highestdensity material consisting primarily of metals such as nickel and iron resides in the central core p 257 0 split into inner core 13 inside the outer core and outer core outer core is liquid inner core is solid outer core is known as mantle OOO ma ntle o rocky material of moderate density mostly minerals that contain silicon oxygen and other elements forms the thick mantle that surrounds the core p257 0 plastic earth39s crust o the lowestdensity rock such as granite and basalt a common form of volcanic rock forms the thin crust essentially representing the world s outer skin 257 0 line outside of the outer circle 0 a few miles thick trivial thickness compared to mantlecore that region around the earth where the earth39s magnetic eld dominates called the magnetosphere each planetstar has this sphere if the north pole of your compass is pointing north it must be pointing to a south magnetic pole because opposite poles attract this eld of the earth has always been changing electrial charges do not like to cross magnetic elds an electron shot towards a magnetic eld will go off in another path most e will get trapped on the magnetic eld lines early 60s late 50s rst experiments were conducted above the earth s atmosphere there are regions of the magnetosphere you run into these are full of electrical charges trapped e and protons the sun is giving off electrons and protons go out through space when they reach the earth39s magnetic eld they get trapped van allen discovered these 39belts39 once they were discovered they were quickly explained solar wind is what causes this ow ofthese particles occasionally on the face of the sun are solar storms great plumes of material are tossed off the sun extra charged particles nd their way into the van allen belts these electrons and protons are orbiting around the magnetic eld lines as they drift along these lines they head for the earth this is where the mag lines come close to the earth when they come into the atmosphere the particles becomes charged and glow this is known as the aurora solar wind Sun gives off electronsprotons that can escape its gravity because of high kinetic energy and temperature charged particles are de ected by other planets magnetospheres causing them to orbit the planets like Earth in belts creates Heliosphere around the solar system aurora Van Allen Belts bands of trapped charged particles along Earth39s equator captured by Earth39s magnetosphere from solar wind trapped charged particles orbit around magnetif eld lines hit into Earth39s atmosphere near the poles excited atoms glow and create Aurora after solar storm Aurora extended to lower latitudes plate tectonics coastline fitting geological evidence supporting the theory proof symmetric magnetic properties on both sides of crack at bottom of Atlantic Ocean interpreted as magnetized mantle material in past motion of two continents moving apart causes crack from plate tectonics can infer continents are moving apart Earth s magnetic eld has reversed many times in the past plates movement is caused by mantle convection currents under Earth s surface material in mantle expands hits surface of crust cools down and sinks down again mountains created by collision of two plates ocean plate moves under continental plate as it pushes upward impact of collision causes earthquakes occur on plate boundaries lower plate melts into hot mantle and pushes up because it is lighter to form a volcano Field reversals when particles react to the local strength of gravity The idea of an electromagnetic field describes how charged particles would respond to forces from other charged particles Studies of lava ows indicate that the magnet field of earth has shifted several times although experts can not surely conclude why Earthquakes the result of a sudden release of energy in the Earth39s crust that creates seismic waves volcanoes an opening up or rupture in a planet s surface or crust which allows hot molten rock ash and gases to escape from below the surface mountains a landform that stretches above the surrounding land in a limited area with a peak continent one of the several large landmasses on Earth oceans major body of saline water atm0sphere ch10 a layer of gas that surrounds a planet or moon usually very thin compared to the size ofthe object Loss of light gases in the earth s atmosphere the energy content is equally partitioned Hydrogen and helium must have traveled above the earth s escape velocity level because they got so hot from the equally distributed energy and they eventually left the earth s atmosphere In a hydrogen atom the protons are heated up so much that they bond into one proton which is lighter than the two separately so it escapes from the earth s atmosphere outgassing the process of releasing gases from a planetary interior usually through volcanic eruptions It can be gradual such as gas escaping from volcano vent or it can be very dramatic such as a volcanic eruption Atmospheric pressure 14 lbsinA2 the earth s atmospheric pressure is l4lbsinA2 and in order to compensate for that the pressure in our body is also 14 lbsinA2 therefore if we were to go under water where the pressure is higher our lungs could collapse If we were to go into outer space where the pressure is lower the organs in our body could potentially explode Water carbon dioxide the earth s original atmosphere was believed to be carbon dioxide because they atmospheres of Venus and Mars are largely carbon dioxide The reason our atmosphere is no longer largely carbon dioxide is because it was mostly dissolved into the oceans But the water can only dissolve so much and therefore living creatures had to take in carbon dioxide as well Effects of living organisms Some of the carbon dioxide in the Earth s original atmosphere probably dissolved in oceans but not all because they would become saturated Creatures like plankton use carbon dioxide to make shells and when they die the shells fall to the bottom of the ocean and turn into limestone rock allowing ohte ocean to absorb more In addition plant growth releases oxygen into the atmosphere It is in this way that the phrase quotwe made our own atmospherequot makes sense Living organisms greatly contributed to the transformation of our atmosphere from one made of carbon dioxide to one made up of oxygen and nitrogen gt greenhouse gases loss of ozone Greenhouse gases are gases that allow visible light energy to pass through them like glass but when that visible light energy heats up the surface the infrared light that s trying to leave the surface to cool it cannot pass back through the gas so inside is much hotter than outside think car in sunlight in middle of summer Greenhouse gases such as carbon dioxide methane and water vapor absorb infrared light emitted from a planet s surface they act like a blanket warming the planet s surface Human produced chemicals known as CFCs were causing great damage to the ozone layer but the nations of the world agreed on a series of treaties that ultimately phased those chemicals out of production As a result the ozone layer is beginning to recover from its earlier damage gtgtchicken little effect Chicken Little was a young chicken in a children s story that felt a drop of rain and thought that the sky was falling He went around and got everyone excited and worried before he found out that his warnings were unnecessary I simply make the point that there is the possibility of that happening in regards to the quot global warmingquot situation gt Moon terminator limb tidal coupling At Gibbous moon you can see a lot of detail about the moon the shadow line is called the terminator The edge of the disc image of the Sun that we see is called the limb Tidal coupling is when two objects are moving or have moved into a synchronus relation with each other because of the tides that each produces on the other The fact that the moon is in such a situation is because of the tides that the earth produces on the moon The same is happening to the earth which will eventually rotate with the moon M00n density 33 gcmA3 craters occur after objects strike the surface rays ejecta Streaks that are a product of the collision re ecting light and appearing to come out of the craters maria Type of crater formed by ancient volcanic eruptions and cratering after the lava reached the surface rilles Long narrow depressions in the lunar surface that resemble channels mountains highlands Relatively lightcolored regions on the surface of the Moon which are elevated several kilometers above the maria Also called terrae difference between near and far sides of the moon Back of the moon has no maria is fully cratered Back of the moon has a large crater with 3 craters in it like a bullseye Age earthmoon 45 billion yrs Modern geologists and geophysicists consider the age of the Earth to be around 45 billion years The planets began to accrete in the solar nebula about 45 bil yrs ago a fact we determine from radiometric dating of the oldest meteorites The formation of the Moon is believed to have occurred 4527 i 0010 billion years ago about 30750 million years after the origin of the Solar System Origin ssion capture co creation condensation collision large impact 3 theories of the existence of the moon 1 Fission theory the earth forms and is spinning fairly rapidly differentiates a bulge develops on one side of the earth bulge pulls off and thrown into spacematerial solidifies and becomes the moon Theory propagated before plate tectonics section from where moon was pulled loose the pacific ocean doesn t t work anymore with plate tectonics 2 Capture theory somewhere btwn mars and Jupiter near a thing of 3 density somehow moon gets deviated in orbit crosses path of earth and its gravity catches it Deals with problem of being in the ecliptic however its very dif to have those kind of things happen hard to deviate that much out of orbit How do u get earth to capture somethingcapture theory could explain density and ecliptic lost favor bc difficult to get it to work dynamically Moon much too large to have been captured by asmall planet like Earth 3 Most accepted theory collision theory earth differentiated same region of earths objects smaller thing forms after earth differentiates object collides with the earth knocks of pieces of the earth into space from the outer part of the earth on average crust has a lower density than average density of the earth pieces of earth and object y off into space lots of dif orbits more of less in the ecliptic began to collide and coalesce come together and form moon makes orbit rather circular lower density than the earth Seems to explain most of what we see with the moon Mercury tidal coupling When one celestial body orbits another tidal forces tend to equalize the rotational periods so that after a very long time they may become identical This end result is called tidal coupling Rotates on its own aXis rotation period is 59 days 88 X 2 176 and 59X 3 177 2 to 3 phase lock with the sun turn on aXis 3 times every time goes around sun twice A tidally locked body takes just as long to rotate around its own aXis as it does to revolve around its partner This synchronous rotation causes one hemisphere constantly to face the partner body Until radar observations in 1965 proved otherwise it was thought that Mercu was tidally locked with the Sun Instead it turned out that Mercury has a 32 spin orbit resonance rotating three times for every two revolutions around the Sun the eccentricity of Mercury39s orbit makes this resonance stable The original reason astronomers thought it was tidally locked was because whenever Mercury was best placed for observation it was always at the same point in its 32 resonance so showing the same face which would be also the case if it were tidally locked Moon like surface eaIth like density Mercury has a surface similar to the moon with craters maria and higlands and a density similar to earth 55 gcmA3 because it diffenrentiated similar to Earth craters small maria highlands like the moon Mercury has these features on its surface maria dark area lava ow highlands mountains weak magnetic eld Mercury has a weak magnetic field VENUS ea1th ike cloud cover little vapor in clouds clouds are made of sulfuric acid plants and water do not eXist Venus as a whole is similar in size gravity and composition to Earth slow retrograde rotation Venus year 244 days Venus rotates very slowly and in retrograde Venus orbit is the closest to being circular out of all the planets atm0sphere carbon dioxide H2SO4 the atmosphere acts as a green house When the sun hits Venus Venus cools off by releasing clouds Venus has a very dense atmosphere which is made mainly of Carbon Dioxide and some nitrogen Above the Gr emhnuse Erreet presenee of co2 a greenhouse gas tn Venus atmosphere sunlrght hll urF heatradlatlon that can t radlate b eyery planet wth co2 atmosphe aek through co2 lncreaslng temperatures oeeurs on re w h h t m r I C Kelvin K Temperature on Venus 750 KelVln900 Fahrenhert energy ofan object as temperature really ls just ameasure of energy 0 KelVln e273 Celslus so add 273 to atemperature measuredln Celslus to know whatrts KelVln equryalent ls L r w h me no longer melts 0 body temperature 7 00 freezlng 32 bolllng e 212 a 100 lelslons on Fahrenhert seales mg pol nt 0 bolllng 100 a 100 lelslons on Celslus seale me craters vnlcanism emst on surface ofVenus Venus Presenee ofclouds eledto bellefthat surface was ajungle 0 Actually de llquld due to Greenhouse effectfrom hlgh eoneentratr on of co 0 Free prtauon from elouds wouldbe acldraln Sulfun Aerd nothqurd water 0 ee temperature ranges from 740 e 750 KelVln 900 F Russlan probes were ent o take pretures o A e for flrst prob s Venus to ldram dlssolV dparaehute e o Seeond probe made rtto surface took afew pretures andthen melted usslan Ameneans erreumyentedthe problem by sendlng a satelhte to orbrt Venus and take pretures to form a topographreal map Venus has eraters o raters on mner planets leads us to behave thatEarth should have eraters too but we don39 ason we don39t see eraters on Earth ls beeause we have atmosphere tmosphere burns up asterords Eroslon due to ram and freezlng remoye eyrdenee of rmpaets Venus rotates slowly and baekward o Dlscoveredbyradar l o Ongrnalwayelength o Re eeted wavelength Showed slow rotauon I We discovered it rotated backwards after WWII because of the enhanced radar technology less dispersion of wave when sent off into space Venus has little to no magnetic eld Mars 2quotd closest planet to us 0 Venus comes within 35 of an AU 0 Mars comes with 12 of an AU Reddish Brown 0 Iron Oxide Rust Deep Valley 0 2000 miles long dwarfs Grand Canyon Large volcano bigger than any on Earth 0 Called Mt Olympus Low pressure atmosphere 0 Water would evaporate immediately 0 Suggests no liquid water on Mars Purcival Lowell Famous Astronomer 0 Drew a picture of Mars with lines and dark spots I He called lines canals I Thought dark spots were cities 0 Mars has tilt similar to Earth so seasons are similar too I Surface changes color depending on the season I Lowell though this was plant growth 0 Poles have ice I Canals used to carry water to ancient cities Later we sent telescope up to Mars and found none of what Purcival claimed 0 Due to seeing and human mind Lowell s story 0 seeing is the focusing and defocusing of an image due to the uctuating atmostphere 0 Mind looks for patterns so Lowell saw canals because it was familiar to him Landers scooped dirt and sprinkled it with water to see if organisms existed Strong evidence for liquid water in past Also evidence of life because unnaturally occurring chemicals were found on the surface Water is probably underground tundra Ice caps grow when in winter and retreat in summer 0 Due to settling of C02 Dry Ice 0 Permanent ice caps are water Pictures of rivers with tributaries and deltas o In order to have rivers you must have rain 0 Evidence suggests Mars had a think atmosphere at one time 0 Mars has NO magnetic eld weak carbon dioxide atmosphere Basically weak carbon dioxide 9 not able to get the same magnitude of greenhouse effect like that of Earth so unable to sustain life Early in history Mars was much more like Earth As with Earth almost all of its carbon dioxide was used up form carbonate rocks But lacking the Earth39s plate tectonics Mars is unable to recycle any of this carbon dioxide back into its atmosphere and so cannot sustain a signi cant greenhouse effect This is why Mars does not have a thick atmosphere like we do Since the atmosphere is extremely thin there is very low atmospheric pressure on the surface And in this kind of low pressure water would immediately evaporate no magnetic eld Large but not global weak magnetic fields exist in various regions of Mars These are unlike the Earth39s global protective magnetic shield reddish color iron oxide The red color that we see is iron oxide rust There is a lot of iron oxide in the soil of Mars this is what gives the reddish brown color large volcanoMt Olympus is on Mars and is the largest volcano in the universe it is larger than any volcano on Earth Waterbecause of the extremely thin atmosphere which also causes dust storms there is very low atmospheric pressure on Mars and no liquid water exists Any water on Mars would evaporate immediately There is strong evidence for liquid water in the past because of meanders and evidence of a delta on Mars It is probably still there but now frozen since Mars is a tundra 2 polar caps contain water ice in a permanent snowice cap The CO in the atmosphere freezes to create dry ice The atmosphere today is too thin to produce a water cycle Mars temperature cooled so water vapor froze and caused lower pressure quotJonathan Swif quotauthor of Gulliver s Travels which described astronomers that described two moons on Mars one that goes faster than the planet actually turns and the other that is slower and appears to go in the opposite direction Coincidentally astronomers discovered 2 moons on Mars that match these characteristics Deimos Tremblingsmaller moon of Mars that is further out than Phobos Ph0b0s Fearwlosest to Mars with some craters a few hundred miles across It encounters some of Mars atmosphere because it is so close which removes some of its energy from its orbit Phobos spirals gradually closer to Mars and will eventually crash because it is not a permanent Moon Neither of Mars planets is big enough to pull itself into a sphere Because of the Asteroid Belt it may depend on when you look at Mars if you want to determine how many moons it has CHAPTER 11 Ch 1 l Jupiter atmospheric bands red spot rapid rotation oblate strong magnetic eld JUPITER Jupiter is oblate because it rotates every 95 hours Mass of Jupiter is 300 times mass of Earth Great Red Spot Discovered in late 1600s still visible today size of 3 Earths diameter Jupiter has 4 major moons Very thin ring system Most of Jupiter s moons probably formed in a similar way that planets formed around Sun in disc of material around Jupiter small lumps formed Roche limit Small lumps held together by their own selfgravity move big lump closer to larger object side of small lump closer to big object will be pulled harder than other side Eventually the tidal pull of the large object will exceed the small object s selfgravity and pulls it apart at a certain DISTANCE which is the Roche limit Outside of Roche limit are moons and inside it are particles making a ring around the planet we would expect to nd small particles inside Jupiter s Roche limit Humans are not held together by selfgravity but by molecular bonds Things can eXist inside the Roche limit but they have to be held together by something other than selfgravity 0 Diameter of Jupiter is 11 times the diameter of the earth Mass is 300 times that of earth Jupiter has bands on it Cloud hops Go deeper and deeper and deeper 9 pressure gets higher higher and higher 0 Early on when people started looking at it with telescope 9 what they found is over here on one side of the planet there is a red spot 0000 If you look at it in detail central region 9 looks like gas put not circling out side of spot 9 looks like it is circling similar to hurricane BUT IT S HUGE Some kind of atmospheric storm 9 some characteristics of a hurricane When you get closer to planet 9 there are all kind of spots Atmosphere is very active 9 rapid rotations OO o Moons are orbiting the planet 0 Jupiter has a strong magnetic eld 9 magnetic elds extends out very far I So far that couple of these moons are moving in the magnetic eld of Jupiter itself 0 Jupiter also has a very thin ring system Roche Limit The distance around a planetlarge object that marks the point where objects held together by self gravity will be pulled apart by the planetlarge object s tidal forces Things can exist within the Roche limit as long as they aren t held together by selfgravity ie we exist within Earth39s Roche Limit all of the Jovian planets rings are within Roche Limit Moons outside of Roche Limit Many moons 4 Galilean moons Io Europa Gamymede Callisto lots of other moons some captured from Asteroid Belt 7 this explains their retrograde motion Caist0 bright spots ice cover Farthest Galilean moon out covered in clear ice no evidence of liquid water reddishpurple ground Tolbert thinks this moon is Beautiful Bright spots on surface are craters About same size as Mercury 3rd largest moon in solar system 2nd largest Jupiter moon Ganymede Big completely covered in ice Parallel grooves because of freezing and thawing which makes a grooved terrain Keeps the same face towards Earth at all times Europa White background brown cracks looks like bloodshot eyeball Chunks of ice lce chunks break up and material from under the ice comes up ice is not sitting on a solid surface Ice is not sitting on solid surface but floating on liquid water Could be organisms in the water 2 techniques to test to find organisms put a lander on the surface and drill down through 1 2 miles of ice to get a water sample then lander does the test and sends back ndings to earth send a sample of the water back to earth to do tests there lo Is the closes moon to Jupiter and the smallest Red background white and dark spots Has an active volcano so interior is molten and pushes up through the surface Mostly sulfur color depends on temperature at which the molten lava hardens Completely liquid all the way through besides a very thin hard crust Similar to earth but lo39s crust is much thinner Crust is too thin to hold up a mountain volcano so it39s more like a geyser Very cold and far away from the sun so heat source is an elliptical orbit around Jupiter and the distance from Jupiter is constantly changing so the tidal pull from Jupiter is very strong Constantly stretched and relaxed and heated up by tidal action Locked in one side of itself to Jupiter Face is sometimes close and sometimes far from Jupiter Captured Moons Has around 60 other captured moons All are small and not unique Captured asteroids don39t come from the development of Jupiter itself but from capturing asteroids from the asteroid belt which is why they go around clockwise At the edge of the moon system several moons orbit in clockwise direction backwards SATURN Low Density Oblate Satum s density is less than one which makes it quot oatquot The planet is oblate because it is rapidly rotating on its axis and its very big Inte139ior similar to Jupiter It is a jovian planet and is made up of mainly gas like jupiter Magnetic Field 8000K stronger than the Earth s magnetic eld but only half the power of Jupiters Shadow Bands There are dark protrusions over Saturn s ring system as the ring moves from behind Saturn to the front of the planet These shadow bands eventually disappear as the ring system moves to the front of the planet It is peculiar that these black bands stay together as the ring moves because we would expect that since the particles at different distances are moving at different speeds the shadow bands would disintegrate and move with these particles Many moons Saturn has many moons but the only two Tolbert discussed are Mimas and Titan Mimas is Satum s first moon and it is responsible for the Cassini Division the period is Mimas is 2 times the period of the Cassini Division Titan is discussed in the next point on the concept list Saturn s Titan Titan is one of Satum s moons It is the only moon we know of that has its own atmosphere and it is covered in clouds There is a lot of evidence of liquid ammonia and ethane on Titan which would give Titan a gooey ethane ocean URANUS DISCOVERED Uranus was the first planet to be quotdiscoveredquot whereas the other planets were visible with the naked eye and therefore had been known about for a very long time Uranus was discovered by Herschel who was looking for comets AXIAL TILT PECULIAR AXIAL ROTATION Uranus is tipped on its side Could be rotating according to the right hand rule tipped 98 or according to the left hand rule tipped 82 depending on how you look at it Due to the axial tilt the seasons are very extreme LIQUID HYDROGEN HELIUM ICES ROCKY CORE Uranus is mainly composed of hydrogen helium hydrogen compounds and methane The hydrogen compounds were formed far enough away from the sun that they formed ices The ices are mixed with smaller amounts of rock and metal Uranus39s Rings Discovered by observations of a stellar occultation in which quotstarquot blinked multiple times which indicated that the star was passing 9 rings eliptical of uranus runs in front of a star stars go behind each ring and therefore there is a drop in light thin rings Uranus39s many moons overall there are 27 moons of uranus ve are massive enough to be called dwarf planets Miranda very small has a cliff with a 12 mile drop which is the tallest drop found in the solar system Off center magnetic eld instead of having a magnetic field set up by the spinning of the planet it is offcentered The magnetic field is closer to the equator than to its poles the magnetic field wobbles back and forth as the planet spins NEPTUNE AdamsLevrerrier After the discovery of Uranus astronomers noticed that is deviated from Newton s Laws Adams calculated what would cause these deviations Figured out that there was a planet further out than Uranus and this was causing this 0 Adams calculated location and mass of this planet He then wrote a paper He was not very credible so the Astronomer Royal decided that Adams needed to find the planet before it could be published 0 Somewhere else Levrerrier was making a map of the sky with the stars and their brightness s on it still exists 0 Royal sent the information to John Gottfried this area had already been plotted so they confirmed that there was a planet After this Levrerrier published a paper saying that he had discovered this planet Royal said that their guy Adams had come up with it first Now both are credited with it o This planet was Neptune similar to Uranus 0 both were discovered 0 both are gas planets and have rings 0 Uranus and Neptune39s inner composition are similar to each other and have two layers an inner core and outer layer of gaseous hydrogen 0 Both have offcenter magnetic fields Magnetic field offcenter o It is tilted relative to its rotational axis 0 The similarity to Uranus proves that Uranus offcenter magnetic field is not due to its extreme axial tilt Neptune Discovery People started to watch the orbit of Uranus to see if it followed Newton s laws and people found out that Uranus did not follow Newton39s laws 1 A young mathematician named Adams took the data on the orbit of Uranus took the deviations of Uranus and calculated what could cause these deviations Adams then found that there had to be another planet yanking on Uranus whose gravity altered Uranus39 orbit Adams sent this paper to be published through the Astronomer Royal The Astronomer Royal wanted to get this clari ed rst but never got around to publishing it N A young astronomer in France Leverrier found similar evidence as Adams and didn t have much trouble getting his work done Leverrier wrote to a colleague at Bonne where they started to prepare a map of the sky Leverrier then looked at a point in the sky where a new object sat and published a paper that announced a new planet 3 Today we credit both Leverrier and Adams with the discovery of Neptune The space program allows us to look close at Neptune which has a deep blue color Large dark spot in the past Neptune used to have a large dark spot on its surface similar to the storm on Jupiter except in color Great dark spot a highpressure storm the quotGreat dark Spotquot has now disappeared didn t last nearly as long as the Great Red Spot did Neptune39s ring The space program has identi ed a very sketchy ring system around Neptune This is not continuous where there are plenty of gaps in the particles Many moons Triton the largest and closest moon going around Neptune The remarkable factor is that triton orbits around Neptune backwardsbackwards the way Neptune rotates and backwards the way the other moons revolve around Neptune Very difficult to explain Can39t use Jupiter s capture theory to explain Off center magnetic field as Uranus It was kind of an accident that Uranus was discovered If there were an extremely dark night and you knew exactly where to look at Uranus and you had good eyes you could see Uranus with the naked eye CHAPTER 12 Dwarf planet PLUTO An object that orbits the Sun and us massive enough for its gravity to have made it nearly round in shape but that does not qualify as an official planet because it has not cleared its orbital neighborhood The dwarf planets of our solar system include the asteroid Ceres and the Kuiper belt objects Pluto and Eris Historically 0 Many objects thought to be planets that now aren t o Vulcan I Looked at the orbit of Mercury more elliptical epsilon of 2 The long axis gradually processed rotated around the Sun Newton s laws could not account for this It was proposed that there must be another planet inside Mercury s orbit closer to the Sun 0 So close to the Sun you couldn t see it This was called Vulcan 0 Thought to exist because it would account for the odd rotation of Mercury 0 When Einstein came up with the General theory of Relativity I Explain when in rotation around very big I Worked out that for the mass of the sun and the distance of Mercury the rotation would process just like it does I Taken as proof for this theory so if there was discovered a planet closer to the Sun then this theory might be considered false By accident Kurshel discovers Uranus but if you look on a totally dark night and you knew where to look you could see it without a telescope It is right on the edge of visibility Because Uranus orbit doesn t exactly follow Newton s Laws so they discovered Neptune So now they do the same thing with Neptune o Perscival Lowell found the canals on Mars waits a little while before trying but follows it for 10 years Thought he saw a deviation so did a calculation so he predicted the mass and location of another planet 0 Built himself an observatory and hired astronomers to photograph the entire sky early 1900s and look for this planet which he was sure it existed I Blink microscopy photographs taken on glass plates Wait a week or so and rephotograph the same piece of sky and then put them together using a machine Looking for the star that appears to jump back and forth rather than blink on and off There were a lot of these that turned out to be asteroids etc but no planets I Lowell dies but the project continues and in 1930 Tombaugh sees a star jump back and forth Turns out that this object is orbiting the sun in a fairly big orbit Announced as Pluto o Orbit is much less circular than most of the other planets crosses Neptune s orbit when it is closest to the Sun 0 Crossed over in 1980 and back across in about 2000 I Turns out the Percival Lowell was wrong It is about 10 up in the ecliptic higher than all others so orbital plane is tilted 17 from ecliptic Also there is no measurable deviation from the Orbit of Neptune so incorrect observation 0 Made a mathematical error 0 Also had insufficient data 0 Based on this prediction the tedious research project started which eventually discovered Pluto I When it crosses Neptune s orbit it crosses away above the orbit so it is nowhere near Neptune Mass also is vastly too small to have any gravitational effect on Neptune More like a moon in size than a planet Crosses the orbit of planet Also a moon rotating the wrong way around the planet 0 Theory that there were two planets around Neptune lnteract resulting in one going backwards and the other being thrown out of orbit Pluto o rejected 0 1935 Discovered the Pluto had its own Moon therefore it can t be the lost moon of Neptune o Considered a planet until 2003 when the lAU met in Prague and decided to demote Pluto to a dwarf planet 0 Issues I Several other objects in this general region 0 Either have to name them as planets or unname Pluto I Distinctly different from all other outer planets 0 Basically ice 0 Very small I Orbit not in the ecliptic 0 Not circular orbit o Caused a big stir so there is a formulation which astronomers now accept to define a planet I An object that is big enough to pull itself into a spherical shape I Has to primarily orbit the sun I Has to have cleared out its orbital path 0 No other objects in the same general orbit Charon o Pluto s relatively large moon 0 Discovered in 1978 o Pluto has two other moons that are much smaller
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