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D A C A • First, Introduction Histor 2 3–2 n Satur , upiter J , Mars , planets th 7 ⇒ Ear = , . us us planet? en an a V planet , Ur a is y of ers v What Mercur : disco definition the planets 6 at Herschel round: look kg to bac Wilhelm ical need ALEX O AN IC D R R

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D A C A • • First, Introduction Histor 3 3–2 n Satur , upiter J , Mars , planets th 7 ⇒ Ear = , . us us planet? en planets an a V planet 8 , Ur a is y ⇒ of ers = v What Mercur : disco Ceres definition the planets Piazzi: 6 at Herschel round: look kg to bac Wilhelm Giuseppe ical need ALEX O AN IC D R R

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D A C A • • • First, Introduction Histor 4 3–2 n “asteroid”. Satur , m ter upiter J , coins Mars , planets th 7 Herschel ⇒ , Ear = , . us us planet? en planets an planets a V planet 8 , Ur 9 a is y ⇒ of ⇒ ers = = v What Mercur : allas disco Ceres P definition the planets Piazzi: 6 at Olbers: Herschel round: ich look kg to bac Wilhelm Giuseppe Heinr ical need ALEX O AN IC D R R

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D A C A • • • • First, Introduction Histor 5 3–2 n “asteroid”. Satur , m ter upiter J , coins Mars , planets th 7 Herschel ⇒ , Ear = , . us us planet? en planets an planets a V planet 8 , Ur 9 a is y planets ⇒ of ⇒ ers = 10 = v ⇒ What Mercur = : allas disco Ceres P definition uno J the planets Piazzi: 6 at Olbers: Herschel round: ich Harding: look kg l to bac Wilhelm Giuseppe Heinr Kar ical need ALEX O AN IC D R R

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D A C A • • • • • First, Introduction Histor 6 3–2 n “asteroid”. Satur , m ter upiter J , coins Mars , planets th 7 Herschel ⇒ , Ear = , . us us planet? en planets planets an planets a V planet 8 , Ur 9 11 a is y planets ⇒ of ⇒ ⇒ ers = 10 = v = ⇒ What Mercur = : allas esta disco Ceres P V definition uno J the planets Piazzi: 6 at Olbers: Olbers: Herschel round: ich ich Harding: look kg l to bac Wilhelm Giuseppe Heinr Kar Heinr ical need ALEX O AN IC D R R

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D A C A • • • • • • First, Introduction Histor 7 3–2 n “asteroid”. Satur , m ter upiter J , coins Mars , planets th 7 Herschel ⇒ , Ear = , . us us planet? en planets planets an planets a V planet 8 planets , Ur 9 11 a is y planets ⇒ 12 of ⇒ ⇒ ers = 10 = v = ⇒ ⇒ = What Mercur = : allas esta disco Ceres P V definition uno J Astrea the planets e: Piazzi: k 6 at Olbers: Olbers: Herschel round: ich ich Harding: Henc look kg l l to bac Wilhelm Giuseppe Heinr Kar Heinr Kar ical need ALEX O AN IC D R R

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D A C A • • • • • • • First, Introduction Histor 8 3–2 n “asteroid”. Satur , m ter upiter J planets , coins 13 Mars ⇒ , planets = th 7 Herschel ⇒ , Ear = , . us Neptune us planet? en planets planets an planets a V ers planet 8 v planets , Ur 9 11 a is y planets ⇒ 12 of ⇒ ⇒ ers = 10 = v disco = ⇒ ⇒ = What Mercur = : allas esta disco Ceres Galle P V definition uno J ied Astrea the planets e: Piazzi: k 6 at Olbers: Olbers: Herschel Gottfr round: ich ich Harding: Henc look kg l l to bac Wilhelm Giuseppe Heinr Kar Heinr Kar Johann ical need ALEX O AN IC D R R

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D A C A • • • • • • • • First, Introduction Histor 9 3–2 n “asteroid”. Satur , m ter upiter J planets , coins 13 Mars ⇒ , planets = th 7 Herschel ⇒ , Ear = , . us Neptune us planet? en planets planets an planets a V ers planet 8 v planets , Ur 9 11 a is planets y planets ⇒ 12 of ⇒ ⇒ ers = 14 10 = v disco = ⇒ ⇒ ⇒ = What Mercur = = : allas esta disco Ceres Galle P V definition uno J ied Astrea Hebe the planets e: e: Piazzi: k k 6 at Olbers: Olbers: Herschel Gottfr round: ich ich Harding: Henc Henc look kg l l l to bac Wilhelm Giuseppe Heinr Kar Heinr Kar Johann Kar ical need ALEX O AN IC D R R

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D A C A • • • • • • • • • First, Introduction Histor 10 3–2 n “asteroid”. Satur , m ter upiter J planets , coins 13 Mars ⇒ , planets = th 7 Herschel ⇒ , Ear = , . us Neptune us planet? planets en planets planets an planets a V ers planet 8 v planets , 15 Ur 9 11 a is planets y planets ⇒ 12 ⇒ of ⇒ ⇒ ers = 14 10 = = v disco = ⇒ ⇒ ⇒ = What Mercur = = : allas esta disco Metis Ceres Galle P V definition uno J ied Astrea Hebe the planets e: e: aham: Piazzi: k k 6 at Olbers: Olbers: Herschel Gr Gottfr round: w ich ich Harding: Henc Henc look kg l l l to bac Wilhelm Giuseppe Heinr Kar Heinr Kar Johann Kar Andre ical need ALEX O AN IC D R R

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D A C A • • • • • • • • • • First, Introduction Histor 11 3–2 n “asteroid”. Satur , m ter upiter J planets , coins 13 Mars ⇒ , planets = th 7 Herschel planets ⇒ , Ear = , . 16 us Neptune us planet? ⇒ planets en planets planets = an planets a V ers planet 8 v planets , 15 Ur 9 11 a is planets y planets ⇒ 12 ⇒ of ⇒ ⇒ ers = 14 10 = = v disco = Hygiea ⇒ ⇒ ⇒ = What Mercur is: = = : allas esta disco Metis Ceres Galle P V definition uno J ied Astrea Hebe Gaspar the planets e: e: aham: Piazzi: k k 6 de at Olbers: Olbers: Herschel Gr Gottfr round: w ich ich Harding: Henc Henc look kg l l l to bac Wilhelm Giuseppe Heinr Kar Heinr Kar Johann Kar Andre Annibale ical need ALEX O AN IC D R R

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D A C A • • • • • • • • • • • First, Introduction Histor 12 3–2 n “asteroid”. Satur , m ter upiter J planets , coins 13 Mars ⇒ planets , planets = th 7 17 Herschel planets ⇒ , Ear ⇒ = , . = 16 us Neptune us planet? ⇒ planets en planets planets = an planets a V ers planet 8 v planets , 15 Ur 9 11 a is planets y planets thenope ⇒ 12 ⇒ of ⇒ ⇒ ers ar = 14 10 = = v disco = Hygiea P ⇒ ⇒ ⇒ = What Mercur is: is: = = : allas esta disco Metis Ceres Galle P V definition uno J ied Astrea Hebe Gaspar Gaspar the planets e: e: aham: Piazzi: k k 6 de de at Olbers: Olbers: Herschel Gr Gottfr round: w ich ich Harding: Henc Henc look kg l l l to bac Wilhelm Giuseppe Heinr Kar Heinr Kar Johann Kar Andre Annibale Annibale ical need ALEX O AN IC D R R

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D A C A • • • • • • • • • • • • First, Introduction Histor 13 3–2 n “asteroid”. Satur , m ter upiter planets J planets , 8 coins 13 ⇒ = Mars ⇒ planets , planets = th 7 17 Herschel planets ⇒ , Ear ⇒ planets = , . = 16 us Neptune us not planet? ⇒ planets en planets planets = an planets a V ers planet 8 are v planets , 15 Ur 9 11 a is planets y planets thenope ⇒ 12 ⇒ of ⇒ ⇒ ers ar = 14 10 = = v disco = Hygiea P ⇒ ⇒ ⇒ = What Mercur is: is: = = : Asteroids allas esta disco Metis Ceres Galle P V definition uno J ied Astrea Hebe Gaspar Gaspar the planets 1800s: e: e: aham: Piazzi: k k 6 de de at Olbers: Olbers: Herschel Gr Gottfr late round: w ich ich Harding: Henc Henc look in kg l l l to bac Wilhelm Giuseppe Heinr Kar Heinr Kar Johann Kar Andre Annibale Annibale ical need ALEX O AN IC D R R

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D A C A • • • • • • • • • • • • • First, Introduction Histor 14 3–3 planets 9 ⇒ = km) planet? a 2400 is = d ( What Pluto ombaugh: T Clyde

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D A C A • Introduction 15 3–3 km) 1300 ∼ d ( planets 9 ⇒ = Quaoar km) planet? 50000 a 2400 is wn = d ( Bro What Pluto Michael & ujillo ombaugh: r T T Clyde Chad

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D A C A • • • Introduction 17 3–3 km) 1300 km) km) ∼ d ( planets 2400 1800 9 ∼ . ⇒ d d ( = ) Quaoar . km) km planet? “Xena” 50000 a 2400 is (1200 wn = (aka d ( Bro What Sedna UB313 Pluto Michael 2003 90377 & al.: al.: ?!? is ujillo ombaugh: r et et T Er T wn wn planets Clyde Chad Bro Bro 136199 10

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D A C A • • • • Introduction 18 3–3 km) 1300 km) km) ∼ d ( planets objects 2400 1800 9 ∼ . ⇒ d d ( = ) Quaoar . km) km planet? “Xena” ansneptunian 50000 a tr 2400 is (1200 wn = (aka ing d ( er Bro v What Sedna UB313 Pluto disco Michael of 2003 90377 & al.: al.: ?!? is ujillo ombaugh: r et et T Er T frequency wn wn planets Clyde Chad Bro Bro High 136199 10 :

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D A C A • • • • • Introduction 19 3–3 , ly km) Assemb 1300 km) km) al ∼ d ( planets objects 2400 1800 9 Gener ∼ . ⇒ d d ( = ) Quaoar . Union planet km) km a planet? “Xena” of ansneptunian 50000 a tr 2400 is (1200 wn = (aka ing d ( er Bro Astronomical v Definition What Sedna 6: UB313 Pluto disco Michael of national and 2003 90377 & Inter al.: al.: ?!? is ujillo ombaugh: r et et GA26/5 T Er T frequency 2006: wn wn planets Clyde Chad Bro Bro High 136199 10 : planets ague

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D A C A • • • • • = = Introduction 3±3 RESOLUTION 5 Definition of a Planet in the Solar System

Contemporary observations are changing our understanding of planetary systems, and it is important that our nomenclature for objects reflect our current understanding. This applies, in particular, to the designation "planets".The word "planet" originally described "wanderers" that were known only as moving lights in the sky. Recent discoveries lead us to create a new definition, which we can make using currently available scientific information.

The IAU therefore resolves that planets and other bodies, except satellites, in our Solar System be defined into three distinct categories in the following way:

(1) A planet1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-g ravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-g ravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects 3, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

1 The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. 2. An IAU process will be established to assign borderline objects into either dwarf planet and other categories. 3. These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies. 3±3 RESOLUTION 6 Pluto

The IAU further resolves:

Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of Trans-Neptunian Objects1.

1 An IAU process will be established to select a name for this category. Relative sizes of the Sun and the planets Venus Transit, 2004 June 8

Elio Daniele, Palermo 1 3–6 Mars: : th/Moon, planets Ear I of , , “twins”) us w en types vie V , called er y Ov major o better ks”). Mercur tw : (“roc into th th/Moon Planets Ear (Ear to ial” System w vie er Solar moons errestr similar Ov “T of all no

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D A C A 1. Division Planets: The Inner Planets (SSE, NASA) 3 are 3–8 giants gas of Mars: moons : large th/Moon, planets Ear of III , Sun), “twins”) , . us Neptune: w , en types V us vie , called around y planets an er Ur ial not major Ov systems o n, better ks”). Mercur tw : terrestr (“roc motion Satur moon into , ., e to th th/Moon (i.e Planets Ear upiter J (Ear to ial” xtensiv ucture System : w e of str e vie planets v giants” in er Solar moons errestr similar ha not Planets Ov “T of all no Moons “gas all

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D A C A er 2. 1. v Although Division Planets: The Outer Planets (SSE, NASA) 5 3–10 )  533 949 19 01 45 2 00 88 383 ...... /R 0 0 0 4 9 1 3 0 R 11  107 815 002 000 5 2 055 1 M ...... / 0 0 0 1 0 14 95 17 M orbit) 318 s d th’ h d h h h h d h 6 0 39 9 2 9 7 8 1 Ear ...... t rot 6 9 P I 24 17 23 10 58 16 (wr 243 , − − ties e inclination 094 007 244 046 017 057 049 205 011 ...... 0 0 0 0 0 0 0 0 0 mass : ] orbital Proper 90 40 78 2 00 50 30 00 78 ◦ : ...... [ i M 1 3 0 0 2 1 7 1 i 17 iod iod per [yr] 88 615 000 7 241 4 9 7 per ...... Planets: 1 0 1 0 orb 83 29 11 P 248 163 orbital rotational : : orb rot U] P 723 52 P 000 387 58 2 2 20 1 ...... [A 0 1 1 0 9 5 . D; a 39 19 30 w m orbit 11 vie ♀ Z ' \ Y [ X  ♂ the 10 er adius of axis y × r Appendix Ov n , us ial icity 496 us th . 1 an ALE

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D A A C A : : 1 After a e R Planets:

Mercury: • not much larger than Moon • densest of all terrestrial planets • no evidence for atmosphere • Rotation period: 59 d, 2/3 of orbital period. • surface: impact craters and tectonics • Only information available is from Mariner 10 (three flybys, 1974/1975) • NASA mission “Messenger” (launched 2004 August 3, flyby 2008 and 2009, in orbit from 2011 on)

• ESA Mission Bepi Colombo, planned for ∼ Aug. 2013, arrival Aug. 2019 NASA/USGS Venus: • similar size to Earth, similar structure • insolation ∼2× Earth • very slow rotation (243 d, retrograde; =⇒ no B-field) • very dense atmosphere: surface pressure ∼90× Earth

• atmosphere: 96.5% CO2, 3.5% N =⇒ strong greenhouse effect =⇒ surface temperature ∼460◦C. • acid rain (yes, sulphuric acid!)

ESA/Venus Express

Information mainly from radar surveying from Earth and from Magellan (1990±1994), plus images from Pioneer Venus Probe (1979). Several landings (Venera, 1975/1981). Currently studied by ESA's Venus Express probe (launch April 2005, arrival April 2006). Earth: • double planet system • Earth surface: dominated by plate tectonics, erosion

• atmosphere: 80% N2, 20%O2 =⇒ moderate greenhouse effect =⇒ surface temperature >0◦C. • water present Moon: • very similar to Mercury, overall • Mariae (plains from massive impacts) and impact craters • Rotation synchronous to orbit around Earth

Earth/Moon, seen from Mars (NASA/Malin) Mars: • smaller than Earth • very low density (hρi ∼ 3 g cm−3) =⇒ small core, probably Fe and FexSy, • polar caps, seasons • thin atmosphere, clouds, fog,. . . • water sublimes =⇒ no liquid water today • Volcanism (large shield volcanoes =⇒ no (?) plate tectonics)

• atmosphere: 95% CO2 =⇒ weak greenhouse effect • two moons (captured asteroids)

NASA, Mars Global Surveyor

Early Exploration through Mariner missions and Viking 1 and Viking 2 orbiters and landers in 1970s, recently, strong interest (NASA Mars Global Surveyor [MGS], ESA Mars Express, plus several landers). Currently best surveyed planet except for Earth. The jovian planets, c C.J. Hamilton Jupiter: • Largest planet in solar system • rapid rotation =⇒ severely flattened, banded atmosphere (Coriolis force), Great Red Spot • strong magnetic field (strong radio emission) • atmosphere: 75% H, 24% He (by mass), very close to solar • differential rotation (rotation period 9h50m on equator, 9h55m on poles). • strong magnetic field • four major “Galilean” moons plus 59 small ones (as of Jan. 2005; all are captured asteroids)

NASA/ESA, Cassini-Huyghens

Early Exploration 1970s through Pioneer 11 and 12, and then through the Voyager probes. Extensively studied by NASA's Galileo project (ended 2003 Sep 14). NASA/ESA Cassini, 2004 Oct. Saturn: • six major moons plus 27 small ones (as of • similar to Jupiter, slightly smaller Jan. 2005; mainly captured asteroids) • rapid rotation =⇒ ¯attened, banded • Early Exploration in 1970s with Pioneer 11 atmosphere and 12 and the Voyager probes. • atmosphere: 75% H, 24% He (by mass), Studied since 2004 July 1 by NASA/ESA molecules etc. similar to Jupiter Cassini-Huygens project (duration: four • Rings! years) Uranus: • atmosphere cold (59 K = −214◦C) =⇒ ammonia has frozen out • methane, hydrogen, and helium detected so far (less He than expected from Jupiter and Saturn!) =⇒ bluish color • inclination of rotation axis: 98◦ (“rolling on ecliptic plane”). • small ring system • five major moons in equatorial plane plus 22 small ones (as of Jan. 2004; captured asteroids)

NASA Voyager 2, 1986 Jan 10

Flyby of Voyager 2 in 1986 January, since then only remote sensing via Hubble Space Telescope (HST) and ground based instruments. Neptune: • atmosphere similar to Uranus, but more active; bright methane clouds above general cloud layer • ring system (5 individual rings) • Two major moons (Triton, 2720 km diameter(!) and Nereid 355 km), 11 captured asteroids

NASA Voyager 2

Flyby in 1989 August by Voyager 2, only HST since then (showed in 1995 that dark spot has vanished, detected new storm system) 16 3–21 planets? k? ucture e? or lik the w Str of look pretation with: e? inter v mal? aces ucture str mo nor deal surf ysical olcanism atmospheres v y ph , y nal where? will (again) e w their else w planets inter system vie ucture ucture and tectonics planetar er str str planetar the the that ws planets la solar plate Ov do is do do , s there w w

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