Credit: ESO 再見 「九大行星」 張師良 可觀自然教育中心暨天文館

Credit: KAGAYA

Credit: NASA, ESA, and A. Schaller (for STScI) Xena (2003 UB 313 )

Credit: Jerry Lodriguss Credit: Akira Fujii Dec 29, 2000 Sept 28, 2000

Path of Venus 2004 Credit: Tunc Tezel English “Planet” = wanderer 中文 「行星」 日本語 「惑星」

From Andreas Cellarius Harmonia Macrocosmica, 1660/61

Credit: NASA, JPL Uranus 天王星 William Herschel March 13, 1781 Neptune 海王星 Urbain Le Verrier, John Couch Adams, Johann Galle Sept 23, 1846

Credit: Ryan McDaniel Titius-Bode Law 波德定律 PlanetkT-B rule distanceReal distance Mercury Venus Earth Mars (Asteroid Belt) Jupiter Saturn Uranus Neptune Pluto

Credit: Scott Hudson Jan 1, Ceres 谷神星 Mar 28, Pallas 智神星 Sept 1, Juno 婚神星 Mar 29, Vesta 灶神星

Credit: NASA Asteroid Belt 小行星帶

Lowell Observatory 羅威爾天文台 Credit: Lowell Observatory Archives Clyde W. Tombaugh 湯博 Credit: Smithsonian Institution Pluto Discovery Plate 冥王星發現底片 Credit: Thomas O'Neil

Blink Comparator Feb 18, 1930 Pluto Discovered!

Radius 半徑 (km) Surface temp 表面溫度 (°C) Axis inclination 自轉軸傾斜 Density 密度 (g/cm 3 ) Rotation period 自轉週期 (hour) Orbital period 公轉週期 (day) Satellites 衛星 ( 夜 ) 430( 日 ) negligible ° Days ° °

Radius 半徑 (km) Surface temp 表面溫度 (°C) Axis inclination 自轉軸傾斜 Density 密度 (g/cm 3 ) Rotation period 自轉週期 (hour) Orbital period 公轉週期 (year) Satellites 衛星 ° ° ° ° °

Earth-like planets / Terrestrial planets 類地行星 Rocky planets 固體行星 Jupiter-like planets / Jovian planets 類木行星 Giants 巨星 太陽 Sun 水星 Mercury 金星 Venus 地球 Earth 火星 Mars 木星 Jupiter 土星 Saturn 天王星 Uranus 海王星 Neptune 冥 王 星 Pluto Credit: Calvin J. Hamilton

Credit: Addison Wesley

Credit: Dr. R. Albrecht, ESA/ESO Space Telescope European Coordinating Facility; NASA Charon 冥衛一 ( 查龍 ) Pluto 冥王星 2306 km 1205 km Jun 22, 1978

Credit: NASA/JPL-Caltech/T. Pyle (SSC) Accretion Disk 吸積盤 Planetesimal 星子

Credit: NASA, JPL, JAXA 433 Eros 愛神星 243 Ida and Dactyl 951 Gaspra Itokawa 系川

Credit: Addison Wesley 1 AU 50 AU 6.8 light hours 光時

Credit: KAGAYA Kuipler Belt 凱伯帶 ~ AU Kuiper belt objects (KBOs) Trans-Neptunian Objects (TNOs)

Oort Cloud 奧爾特雲 50,000 to 100,000 AU

1992 QB1 1st KBO Aug 30, AU ? km Credit: David Jewitt

Credit: A. Stern(SwRI), M. Buie(Lowell Obs.), NASA, ESA Pluto 冥王星

The Largest Moons and Smallest Planets Credit: Calvin J. Hamilton

Credit: ESO, ESA, Astrovirtel & G. Hahn (German Aerospace Center, DLR)

Samuel Oschin Telescope Credit: SOT/Caltech

Credit: Misha Gravenor, Discover Credit: Samuel Oschin Telescope Michael E. Brown 1.2m Telescope

Credit: Michael E. Brown Jun 4, 2002 Quaoar 夸奧亞 Nov 14, 2003 Sedna 塞德娜

Credit: NASA/JPL-Caltech/R. Hurt (SSC)

Credit: Michael E. Brown Jan 5, UB 313 Xena 齊娜

Credit: Keck Observatory, NASA, ESA, and M. Brown (Caltech) 2003 UB 313 Keck Observatory ImageHubble Space Telescope Image 2400 km diameter, -240 degree

Credit: NASA, NEOP

Credit: NASA, ESA, and A. Feild (STScI)

Credit: Misha Gravenor, Discover

Credit: Nature

Credit: NASA and G. Bacon (STScI) Quaoar 夸奧亞 "Is it a planet?" and we said: "No, no, it's not a planet. And, by the way, Pluto’s not a planet either"

Credit: NASA/JPL-Caltech/R. Hurt (SSC) Sedna 塞德娜 Then we found Senda. "Is it a planet, is it a planet?" "No, no, it's not a planet. And, by the way, Pluto’s not a planet either"

Credit: Robert Hurt (IPAC) Xena 齊娜 "Is it a planet?"

Is? Or Isn't? Credit: Terry E. Smith Pluto, a planet?

Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team Pluto System 冥王星系統

Credit: JHUAPL/SwRI New Horizons 新視野

Credit:: NASA, ESA, and P. McCullough (STScI) Exoplanet 系外行星 XO-1b Hot Jupiters 熱木星

Credit: NASA/JPL-Caltech/R. Hurt (SSC) 脈衝星 Pulsar 4U What is a planet?

Credit: Don Dixon

Credit: NASA, ESA and G. Bacon (STScI) Option 1: 10 Planets Option 2: 8 Planets

Credit: NASA/FUSE/Lynette Cook Option 3: (a) Not a Star (b) Round Option 4: Subdivide into Rocky Planets, Gas Giants, Ice Dwarfs

Credit: NASA/JPL-Caltech