Juno’s Voyage to JupiterOrbital Motion of Galilean MoonsCourse AnnouncementsAssignmentsBegin Chapter 2Brief Introduction to Chapter 2Historical Sections of Chapter 2Historical Sections of Chapter 2Planetary Motions in the SkyPlanetary Motions in the SkyThe Solar System – Two ConceptsSlide 12Planetary AlignmentsPlanetary motions in the SkyPlanetary Motion in the SkyPlanetary Motion in the SkyPlanetary Motion in the SkyPlanetary Motion in the SkyPlanetary Motion in the SkyPlanetary Motion in the SkyPlanetary Motion in the SkyPlanetary Motion in the SkyPlanetary Motion in the SkyRetrograde MotionThe Copernican UniverseThe Rise of HeliocentrismEstablishing HeliocentrismKepler’s 1st LawKepler’s 1st LawKepler’s 1st LawKepler’s 2nd LawKepler’s 2nd Law – in practiceKepler’s 3rd LawUsing Kepler’s 3rd LawExample 1Example 2Example 3Example 4Planetary MotionJuno’s Voyage to JupiterOrbital Motion of Galilean MoonsMovie captured by Juno – First movie of orbital motion in historyImage Credit: Michael Steginia/Adam Block/NOAO/AURA/NSFCourse Announcements•Quiz 1 TODAY–Given at end of class•Friday, 2 Sept. class cancelled•Extra Credit Sessions have begun. Next opportunity is next week. Be sure to sign up if you want to attend.- Sign up sheets outside of Room 108 in Nielsen Physics and Astronomy.AssignmentsReading Assignments•Chapter 2. Sections 2.5 – 2.8 [Including More Precisely 2-1][Read by Wednesday, 7 Sept.]Parallel Lectures•No new episodesMastering Astronomy•Chapter 1 Homework[Due Wednesday, 31 Aug. at 11:59 PM EDT]BEGIN CHAPTER 2The Copernican RevolutionBrief Introduction to Chapter 2Understanding Planetary Motions•Chapter 1 covered the general motions of the Sun, Moon, and stars in the sky due to Earth’s motions (rotation, revolution, and precession) and the motions of the Moon.•Chapter 2 focuses on understanding the motion of the planets (“wanderers”) in the sky and the physics behind orbital motions.–How to the planets move in the sky as viewed from Earth?–How do the planets move in general (orbital motion)?–A triumph of the scientific method to come to understand the physics of the heavensHistorical Sections of Chapter 22.1 – 2.4 Left mostly for your reading•Material Dr. Lindsay wants you to know–The Geocentric Ptolemaic Model•Difference between geocentric and heliocentric models–Who the following people are (no need to memorize dates), and how they contributed to the rise and acceptance of heliocentrism•Nicolai Copernicus – Pushed heliocentric model to explain retrograde motion of planets•Tycho Brahe – Made the most detailed observations of planetary positions, i.e., generated the necessary data set–This guy is a nut, I highly encourage researching him•Johannes Kepler – Used Brahe’s data to deduce the nature of planetary orbits: Elliptical NOT Circular•Galileo Galilei – Made four fundamental (that means you should know what they are) telescopic observations demonstrating the validity of heliocentrism and the death of holding onto Aristotelian idealsHistorical Sections of Chapter 22.1 – 2.4 Left mostly for your reading•Material Dr. Lindsay wants you to know–The four telescopic observations Galileo made that provided the evidence needed to overturn the most powerful geocentric model called the Ptolemaic modelPlanetary Motions in the SkyThe “wanderers” of the night skyCredit: Yuri BeletskyPlanetary Motions in the SkyOur idea of how Solar System is structured and what physical processes govern planetary motion must include:•“Wandering” nature of planets–Planets always appear close to the Ecliptic–Unlike the stars, planets change position relatively quickly (no fixed RA and Dec.)–Planets appear to move at different speeds at different times–Planets move (west to east) with respect to fixed star background – prograde motion–Mercury and Venus “tethered” to the Sun–Mars, Jupiter, and Saturn exhibit retrograde motion (east to west) and appear brighter during this periodThe Solar System – Two ConceptsPrograde and retrograde motion using heliocentric modelWestEastDeferentsEpicycleEarthSunMarsOrbitsEarthSunMarsGeocentric model Heliocentric modelVenusVenusMars’s orbit is larger – Superior PlanetVenus’s orbit is smaller – Inferior PlanetBoth constructions are flat, which keeps all the planets near the EclipticOption One – Geocentric Solar System: •Earth standing still at the center and everything moving around it•This one that “feels right” as a person standing on the EarthOption Two – Heliocentric Solar System: •Sun at the center of the Solar System and everything orbiting it•Less intuitive, and requires us to be much more clever to realize it is the right structureWhat structure of the Solar System explains all of these apparently complex motions?Planetary AlignmentsSun, Earth, and planets in a line•Opposition occurs at a planets closest approach to Earth (Earth between planet and Sun) –only for Superior planets•Conjunction occurs when a planet appears close to the Sun in our sky–Inferior and Superior planetsOppositions – Opposite; Conjunctions - ConjoinedInferior planet orbit as seen from EarthPlanetary motions in the Sky•Prograde motion is night-to-night eastward motion•Retrograde motion is night-to-night westward motion–During retrograde motion, planets are at their brightest… why?Prograde and Retrograde MotionWestEastPlanetary Motion in the SkyPrograde and retrograde motion using heliocentric model•Prograde motion is night-to-night eastward motion•Retrograde motion is night-to-night westward motion•To understand why these are the motions we observe from Earth, we need to consider where the planets are over several monthsOrbitsEarthSunMarsOrbital Period of Earth: 1 year (365.25 days)Orbital Period of Mars: 684.5 daysBeing further away, Mars orbits slower than EarthPlanetary Motion in the SkyPrograde and retrograde motion using heliocentric modelImagine our view of MarsPoint 1: Time – 0 months11Fixed Background StarsPlanetary Motion in the SkyPrograde and retrograde motion using heliocentric modelImagine our view of MarsPoint 1: Time – 1 month121 -> 2: PROGRADEMore Eastward2Fixed Background StarsPlanetary Motion in the SkyPrograde and retrograde motion using heliocentric modelImagine our view of MarsPoint 1: Time – 2 months1232 -> 3: PROGRADEMore Eastward3Fixed Background StarsPlanetary Motion in the SkyPrograde and
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