Jovian Planets (2010)


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Jovian Planets (2010)

  1. 1. <ul><li>The Jovian Planets </li></ul><ul><ul><li>Jupiter </li></ul></ul><ul><ul><li>Saturn </li></ul></ul><ul><ul><li>Uranus </li></ul></ul><ul><ul><li>Neptune </li></ul></ul>Saturn seen by Cassini
  2. 2. Gas Giant Sizes
  3. 3. Jupiter Data Mean Distance from Sun 483,300,000 miles 5.2 AU Diameter at the Equator 88,700 miles Length of “Year” (revolution around the sun) 11.86 earth years Diameter if Earth = 1 11.19 Length of “Day” 9 hr. 50 min. 30 sec. Mass if Earth = 1 317.83 Symbol Surface Gravity if Earth = 1 2.54
  4. 4. King Planet <ul><li>King of the Gods : Jupiter (Greek, Zeus) was the King of the Gods. Jupiter was the son of Saturn (Greek, Cronus) </li></ul><ul><li>Jupiter is the largest planet in the solar system </li></ul><ul><li>1,400 planet earths would fill Jupiter </li></ul><ul><li>Some of Jupiter’s moons are larger than recognized planets </li></ul>
  5. 5. <ul><li>Discovery : Jupiter is the fourth brightest object in the sky after the sun, moon, and Venus (sometimes Mars is brighter than Jupiter). </li></ul><ul><li>Galileo discovered Jupiter’s four largest moons in 1610 (Io, Europa, Ganymede, Callisto) </li></ul><ul><li>These are referred to as the Galilean moons </li></ul><ul><li>Galilean moons are visible in binoculars and small telescopes </li></ul><ul><li>Moons are in different positions each night </li></ul>Discovery
  6. 6. Galileo’s Sketches Galileo’s telescopes
  7. 7. Jupiter’s Satellites <ul><li>The chart shows the revolutions of Jupiter’s moons </li></ul><ul><li>Along the side are the days of the month </li></ul><ul><li>Visualize a line crossing the chart, the positions where the line crosses the spirals represent the appearance of Jupiter’s moons for that date </li></ul><ul><li>The closest satellite Io forms the smallest spiral pattern </li></ul><ul><li>The farthest satellite from Jupiter, Callisto, forms the largest spiral </li></ul>
  8. 8. Fastest Day <ul><li>Rapid Rotation : One Jupiter day is equal to nearly 10 earth hours—the shortest “day” in the solar system. </li></ul><ul><li>Features on Jupiter appear to move quickly when seen in a telescope </li></ul><ul><li>Rapid rotation creates a squashed appearance </li></ul>
  9. 9. Missions to Jupiter <ul><li>Spacecraft : Pioneer 10 in 1973 and later by Pioneer 11, Voyager 1, and Voyager 2 </li></ul><ul><li>Galileo mission orbited Jupiter for many years (1995—2003) </li></ul><ul><li>Galileo plunged into Jupiter's crushing atmosphere on Sept. 21, 2003 </li></ul>
  10. 10. Gas Giant <ul><li>Gas Planet : Jupiter does not have a solid surface. </li></ul><ul><li>We see the top of Jupiter’s atmosphere </li></ul><ul><li>Jupiter is about 90% hydrogen and 10% helium. </li></ul><ul><li>Similar to the composition of the nebula from which the sun and planets formed. </li></ul><ul><li>Jupiter may have a solid core </li></ul><ul><li>Jupiter radiates more heat back into space than it receives from the sun </li></ul>
  11. 11. Differential Rotation <ul><li>Jupiter’s rotation rate varies with latitude (differential rotation) </li></ul><ul><li>The other gas planets, and the sun, also display differential rotation </li></ul>
  12. 12. Jupiter’s Differential Rotation POLAR REGION ROTATION TIME 9 hours 55minutes EQUATORIAL REGION ROTATION TIME 9hours 50minutes
  13. 13. Cloud Bands <ul><li>Jupiter has high velocity winds (up to 400 mph) confined in wide latitude bands </li></ul><ul><li>The winds blow in opposite directions in nearby bands </li></ul><ul><li>Colors related to composition and temp </li></ul><ul><li>Zones : Light colored bands </li></ul><ul><li>Belts : Dark colored bands </li></ul>
  14. 14. Jupiter’s clouds move in east-west bands Reddish-colored belts alternate with white-colored zones.
  15. 15. Zones & Belts of Jupiter
  16. 16. Great Red Spot <ul><li>Great Red Spot : First observed > 300 years ago </li></ul><ul><li>The GRS is an oval about 7,500 by 15,500 miles, big enough to hold two earths. </li></ul><ul><li>Essentially a region of low pressure, a storm </li></ul>
  17. 17. Jupiter & Ganymede
  18. 18. Voyager’s Great Red Spot
  19. 19. Jupiter’s Magnetism <ul><li>Magnetosphere : Jupiter has an immense magnetic field, much stronger than that of earth. </li></ul><ul><li>It is so large that Jupiter’s moons lie within this magnetic zone. </li></ul><ul><li>Field traps dangerous radiation </li></ul><ul><li>Creates massive auroras, imaged by HST </li></ul>
  20. 20. Jupiter’s Magnetosphere
  21. 21. Jovian Auroras
  22. 22. Another Ringed Planet <ul><li>Jupiter has a faint ring system </li></ul><ul><li>Discovered by the Voyager spacecraft </li></ul><ul><li>All of the Jovian planets possess ring systems (Jupiter, Saturn, Uranus, Neptune) </li></ul>
  23. 23. Galileo Mission: Jupiter’s Rings
  24. 24. The Jupiter Comet <ul><li>Shoemaker-Levy 9 : In July 1994, Comet Shoemaker-Levy 9 collided with Jupiter. </li></ul><ul><li>Discovered in advance </li></ul><ul><li>Impact observed by the Hubble Space Telescope and other instruments </li></ul><ul><li>Jupiter captured the comet into a new orbit </li></ul><ul><li>Comet broke into pieces, each fragment creating a separate impact </li></ul><ul><li>Dark spots created by this collision were visible even in small telescopes and lasted almost one year. </li></ul><ul><li>One of the rarest observations in science </li></ul>
  25. 25. Impact!
  26. 26. Hubble Space Telescope View
  27. 27. SL-9’s Dark Spots (HST)
  28. 28. Jupiter’s Satellites <ul><li>Jupiter has 63 known satellites (As of 2004), the 4 large Galilean moons and 59 small ones. </li></ul><ul><li>Named for characters in the mythology of Jupiter </li></ul>
  29. 29. Satellites Jupiter’s first 16 satellites (in order outward from Jupiter) Galilean Satellites Metis Io Leda Ananke Adrastae Europa Himalia Carme Amalthea Ganymede Lysithea Pasiphae Thebe Callisto Elara Sinope
  30. 30. Moons of the Solar System
  31. 31. Galilean Satellites : Io <ul><li>Io is the third largest satellite of Jupiter </li></ul><ul><li>Io is slightly larger than earth’s moon </li></ul>
  32. 32. Io’s Surface <ul><li>Io displays a young, dynamic, rocky surface. </li></ul><ul><li>The Voyager 1 discovered areas of active volcanism, the first ever discovered on another world </li></ul><ul><li>Io’s volcanoes erupt molten sulfur </li></ul>
  33. 33. Io’s Features <ul><li>Volcanic surface features such as calderas, lakes of molten sulfur, flows of molten sulfur hundreds of miles long, and volcanic vents </li></ul><ul><li>Sulfur and its compounds are colorful </li></ul><ul><li>Io most resembles a cheese pizza </li></ul><ul><li>Io’s volcanism most likely results from Jupiter’s tidal action </li></ul>
  34. 34. Io’s Hellish Surface (Galileo)
  35. 35. Io Volcanism
  36. 36. Io and Jupiter’s Clouds (Cassini) Io by Cassini
  37. 37. Galilean Satellites: Europa <ul><li>Europa is fourth largest satellite of Jupiter </li></ul><ul><li>Europa is slightly smaller than the earth’s moon. </li></ul>
  38. 38. Europa’s Surface <ul><li>Surface : Smooth, frozen water surface </li></ul><ul><li>Young, very few apparent impact craters </li></ul><ul><li>Resembles a billiard ball </li></ul>
  39. 39. Europa’s Water <ul><li>Liquid Water : Europa’s surface resembles sea ice on earth </li></ul><ul><li>Europa might posses an internal layer of liquid water, perhaps as much as 30 miles deep </li></ul><ul><li>Liquid water is an important ingredient for life </li></ul>
  40. 40. Dark Streaks <ul><li>Dark Streaks : Dark streaks crisscross the entire globe of the satellite </li></ul><ul><li>The larger ones are roughly 12 miles across. </li></ul>
  41. 41. Europa
  42. 42. Europa-Surfaces
  43. 43. Dark Streaks on Europa
  44. 44. Ski Europa!
  45. 45. Dive Europa!
  46. 46. Galilean Satellites: Ganymede <ul><li>Ganymede is the largest of Jupiter’s known satellites, and the largest satellite in the solar system. </li></ul><ul><li>Ganymede is larger than Mercury and Pluto </li></ul>
  47. 47. Ganymede’s Surface <ul><li>Icy Surface : Old, icy surface </li></ul><ul><li>Possesses numerous impact craters </li></ul><ul><li>The craters on Ganymede are thought to date from 3 billion years in the past, similar to earth’s moon </li></ul><ul><li>Ganymede also exhibits light colored grooves and ridges </li></ul>
  48. 48. Ganymede’s Craters <ul><li>Formed in ice </li></ul><ul><li>Crater walls slump over time creating “ghost” craters termed palimpsests. </li></ul>
  49. 49. Ganymede
  50. 50. Ganymede Terrain
  51. 51. Enki Catena (crater chain)
  52. 52. Galilean Satellites: Callisto <ul><li>Callisto is the second largest Jupiter satellite </li></ul><ul><li>Slightly smaller than the planet Mercury </li></ul><ul><li>Callisto is about 40% ice and 60% rock and iron </li></ul>
  53. 53. Callisto’s Surface <ul><li>Surface : Ancient surface, saturated with craters </li></ul><ul><li>Resembles highlands on the moon and Mars </li></ul><ul><li>Possibly the oldest unaltered surface in the solar system </li></ul>
  54. 54. Callisto Galileo Probe: Callisto terrain
  55. 55. Galileo: Callisto Terrain
  56. 56. Valhalla <ul><li>Valhalla is a gigantic, multi-ring impact basin nearly 1,900 miles in diameter </li></ul><ul><li>Resembles a bull’s eye </li></ul><ul><li>Similar to Mare Orientale on the moon, and Mercury’s Caloris Basin </li></ul>
  57. 57. Valhalla
  58. 58. Gipul Catena <ul><li>A chain of impact craters </li></ul><ul><li>A series of impacts from a fragmented body </li></ul><ul><li>Similar to the Shoemaker-Levy 9 comet impact </li></ul>
  59. 59. Gipul Catena
  60. 60. Jupiter Family Left to Right : Ganymede, Callisto, Io, Europa
  61. 61. Lore of Jupiter <ul><li>A conjunction of Jupiter and Venus in the year 3 B.C. may have been the inspiration for the famous Star of Bethlehem </li></ul><ul><li>Venus and Jupiter appeared to merge briefly, would have appeared as one incredibly bright star </li></ul>
  62. 62. Star of Bethlehem?
  63. 63. Saturn
  64. 64. Saturn Data Mean Distance from Sun 886,281,264 miles 8.8 AU Diameter at the Equator 74,600 miles Length of Year 29.46 earth years Diameter if Earth = 1 9.41 Length of Day 10 hr, 14 min Mass if Earth = 1 95.16 Symbol (draw) Surface Gravity if Earth = 1 1.08
  65. 65. Ringed Planet <ul><li>Saturn has been known since prehistoric times </li></ul><ul><li>It is visible to the naked eye and resembles a bright, yellow star that doesn’t twinkle </li></ul><ul><li>Saturn is most famous for its system of rings. Galileo first observed Saturn with a telescope in 1610 </li></ul><ul><li>Galileo was unable to see the rings, he thought that the planet had two large satellites resembling ears, a Mickey Mouse world </li></ul>
  66. 66. Cassini: Approaching Saturn
  67. 67. Huygens’ Rings <ul><li>Christian Huygens first correctly described the rings of Saturn in 1659 </li></ul><ul><li>Saturn’s rings remained unique in the solar system until the 1970’s when faint rings were discovered around Jupiter, Uranus, and Neptune </li></ul>
  68. 68. Huygens Discovered Saturn’s Rings Huygens sketch Huygens loooong refracting telescope
  69. 69. Saturn’s Visibility <ul><li>From earth, Saturn appears to slowly drift through the zodiac constellations requiring 29 earth years for one complete revolution </li></ul><ul><li>Throughout its 29 year revolution, Saturn’s orientation allows us to see the top and bottom of the rings, each half is visible for about 14 earth years </li></ul><ul><li>When Saturn appears edge on, the rings appear as a thin line and nearly disappear. This is termed a ring-plane crossing . The last occurred in 1995, we are due for another in 2009 </li></ul><ul><li>Saturn’s synodic period is a little over an earth year long (378 days), this means that Saturn’s oppositions occur every 378 days </li></ul>
  70. 70. Our view of Saturn’s rings during its 30-year revolution around the Sun At some points in its orbit, we see the full face of the rings, and sometimes the rings disappear when we see them edge-on.
  71. 71. Saturn’s Changing Inclination (Friedman, 2004-2007)
  72. 72. Saturn Ring Plane Crossing
  73. 73. Full Moon & Saturn
  74. 74. Missions to Saturn <ul><li>Saturn was first visited by NASA's Pioneer 11 in 1979 and later by Voyager 1 and Voyager 2 </li></ul><ul><li>Cassini (a joint NASA / ESA project) arrived on July 1, 2004 and orbits Saturn </li></ul><ul><li>Cassini released the Huygens probe that landed on Saturn’s moon Titan in January 2005 </li></ul><ul><li>Huygens was able to return images from the surface of Titan </li></ul>
  75. 75. Fast Rotator <ul><li>Like Jupiter, Saturn has a fast rotation of close to 10 hours on earth </li></ul><ul><li>Lightest Planet : Saturn is the least dense of the planets, it is less dense than liquid water </li></ul><ul><li>Like Jupiter, Saturn is composed of gases, there is no solid surface except perhaps at the very center where a solid core is thought to exist </li></ul>
  76. 76. The Lightest Planet <ul><li>Saturn is about 75% hydrogen and 25% helium </li></ul><ul><li>Similar in composition to the supposed nebula from which the solar system formed </li></ul><ul><li>As does Jupiter, Saturn emits more heat back into space than it receives from the sun </li></ul>
  77. 77. Cloud Features <ul><li>Unlike Jupiter, Saturn’s zones and belts are more difficult to see. </li></ul><ul><li>Saturn displays white oval spots on rare occasions. </li></ul>
  78. 78. Cassini: Swirling Storms of Saturn
  79. 79. Ring Features <ul><li>The major divisions of Saturn’s rings are named A, B, and C </li></ul><ul><li>The gap between the A and B rings is named the Cassini division. </li></ul>A B C Cassini Division
  80. 80. Saturn’s Features
  81. 81. Ring Particles <ul><li>Rings appear solid in a small telescope </li></ul><ul><li>Actually made of many small particles each in an independent revolution about Saturn. </li></ul><ul><li>Particles range from less than an inch to several yards </li></ul><ul><li>Each particle a separate “moon” of Saturn </li></ul>
  82. 82. Cassini: Saturn’s Rings
  83. 83. Amorphous Rings <ul><li>Rings: 155,376 miles in diameter, but are less than a mile in thickness. </li></ul><ul><li>All ring particles squeezed together would create a world < 60 miles across </li></ul><ul><li>Ring particles mainly water ice with some rock </li></ul><ul><li>Ring Origins : Probably the breakup of some larger satellites </li></ul>
  84. 84. Cassini Spacecraft Crosses Saturn's Ring Plane
  85. 85. Satellites of Saturn <ul><li>Saturn has 34 named satellites [click] </li></ul><ul><li>The first satellites were discovered by telescopic observers. Later satellites were discovered by space missions </li></ul><ul><li>Saturn’s satellites were named for miscellaneous Greek and Roman mythological characters </li></ul><ul><li>Saturn’s first known moon was Titan, discovered in 1655 by Christian Huygens </li></ul>
  86. 86. First 18 Satellites of Saturn Pan Mimas Helene Atlas Enceladus Rhea Prometheus Tethys Titan Pandora Telesto Hyperion Epimetheus Calypso Iapetus Janus Dione Phoebe
  87. 87. Some Mythology of Saturn’s Moons <ul><li>Pan : Half human, half goat Roman god </li></ul><ul><li>Pandora : Made of clay by Hephaestus at the request of Zeus; she married Epimetheus and opened the box that loosed a host of plagues upon humanity </li></ul><ul><li>Mimas : A Titan felled by Hephaestus in the war between the Titans and Olympian gods. </li></ul>
  88. 88. Mimas <ul><li>Mimas is composed mainly of water ice and a small amount of rock. </li></ul><ul><li>The surface of Mimas is dominated by an impact crater 80 miles in diameter. This crater is almost 1/3 of the diameter of Mimas. </li></ul><ul><li>This crater is named Herschel after William Herschel, the astronomer who discovered Mimas in 1789. </li></ul><ul><li>The rest of Mimas is saturated with craters. </li></ul>
  89. 89. Darth Crater on Mimas
  90. 90. Enceladus <ul><li>Enceladus is the most reflective body of any in the solar system. Its surface is covered with fresh, clean ice. </li></ul><ul><li>Enceladus exhibits smooth plains and liner cracks (tiger stripes) and ridges. </li></ul><ul><li>Much of the surface appears to be geologically young (lacking craters) </li></ul><ul><li>2005 : Cassini imaged fountains of water ice </li></ul>
  91. 91. Fresh Tiger Stripes on Saturn's Enceladus
  92. 92. Enceladus Close-Up
  93. 93. Fountains of Enceladus
  94. 94. Titan <ul><li>Titan is the largest satellite of Saturn, larger in diameter than Mercury and Pluto </li></ul><ul><li>Titan is the second largest satellite in the solar system (after Ganymede). </li></ul><ul><li>Titan is about half water ice and half rocky material. </li></ul><ul><li>Titan has a thick, orange atmosphere of nitrogen </li></ul><ul><li>The Cassini mission landed a probe (Huyghens) on the surface of Titan in 2004 </li></ul><ul><li>Cassini observed stream patterns and shorelines, likely liquid methane </li></ul>
  95. 95. Cassini’s Titan
  96. 96. Three Kilometers Above Titan
  97. 97. Titan’s Surface (Huygens)
  98. 98. Shoreline Terrain on Saturn's Titan (Huygens Probe)
  99. 99. Titan: Stream Beds
  100. 100. Huyghens Landing Movie [ Click ]
  101. 101. Hyperion: Sponge Moon of Saturn
  102. 102. Iapetus <ul><li>Iapetus is the third largest of Saturn’s moons </li></ul><ul><li>One hemisphere of Iapetus is as dark as coal, and the other half is bright </li></ul><ul><li>Resembles yin & yang </li></ul><ul><li>Cassini imaged strange equatorial mountain range, moon resembles a walnut </li></ul>
  103. 103. Saturn's Iapetus: Moon with a Strange Surface
  104. 104. Lore of Saturn <ul><li>Cronus : Saturn, as the outermost of the classical planets, requires the longest time to revolve once around the sun (about 30 years). </li></ul><ul><li>Therefore, the Greek god Cronus (Roman Saturn) was believed to be lethargic and have a dark personality. </li></ul><ul><li>The term saturnine means uncommunicative, melancholy, and slow. </li></ul>
  105. 105. Uranus Data Mean Distance from Sun 1,782,000,000 miles 19.2 AU Diameter at the Equator 31,800 miles Length of “Year” (revolution around the sun) 84.01 earth years Diameter if Earth = 1 4.01 Length of “Day” 17 hr. 14 min. Mass if Earth = 1 14.5 Symbol Surface Gravity if Earth = 1 0.91
  106. 106. First New Planet <ul><li>Uranus : Uranus is the ancient Greek deity of the heavens </li></ul><ul><li>Uranus was the son of Gaia (earth) and the father of Cronus (Saturn) </li></ul><ul><li>First Modern Planet : Uranus was the first planet to be discovered in modern times </li></ul><ul><li>William Herschel discovered Uranus on March 13, 1781 </li></ul>
  107. 107. Observing Uranus <ul><li>Uranus is sometimes just barely visible to the unaided eye on a very clear night </li></ul><ul><li>It is easy to locate with binoculars if you know exactly where to look </li></ul><ul><li>In a telescope, the planet resembles a tiny, green-colored disk </li></ul>
  108. 108. Blue Gas Giant <ul><li>Uranus is a gas giant like Jupiter and Saturn </li></ul><ul><li>The atmosphere of Uranus is composed of 83% hydrogen, 15% helium, and 2% methane </li></ul><ul><li>The methane creates the blue color of Uranus’s atmosphere </li></ul>
  109. 109. Uranus From Earth (Keck)
  110. 110. Voyager 2 <ul><li>Spacecraft : Uranus has been visited by only one spacecraft, Voyager 2 on Jan 24, 1986. </li></ul><ul><li>Voyager revealed Uranus to be a featureless blue disk of gas. </li></ul><ul><li>Voyager also discovered 10 small moons in addition to the 5 large ones already known. </li></ul>
  111. 111. Planet on Its Side <ul><li>Tilted Planet : The rotational axis of Uranus is tilted 98º </li></ul><ul><li>The planet appears to be lying on its side. </li></ul><ul><li>Each pole of the planet is pointed towards the sun for about 42 years, half of a “Uranian” year. </li></ul><ul><li>Why is Uranus tilted so dramatically? The planet may have suffered a collision with an earth-sized object early in its formation </li></ul>
  112. 112. The Uranus axis of rotation is tilted on its side, making seasonal changes drastic.
  113. 113. Axial Tilts of the Planets
  114. 114. Dark Rings <ul><li>Rings : A faint system of rings was discovered in 1977 when Uranus passed in front of a star. </li></ul><ul><li>Voyager 2 photographed the rings in 1986. </li></ul><ul><li>There are 11 known rings, all very faint. The material composing the rings is very dark. </li></ul><ul><li>The rings of Uranus were the first to be discovered after those of Saturn. </li></ul>
  115. 115. Uranus Occultation
  116. 116. Satellites of Uranus <ul><li>Uranus has 20 named satellites plus one recently discovered which has yet to be given a name. </li></ul><ul><li>The satellites are named after characters from the writings of Shakespeare and Pope ( Rape of the Lock ) </li></ul>
  117. 117. Uranus’s Satellites (in order outward from Uranus) Cordelia Portia Ariel Sycorax Ophelia Rosalind Umbriel Prospero Bianca Belinda Titania Setebos Cressida 1986U10 Oberon   Desdemona Puck Caliban   Juliet Miranda Stephano  
  118. 118. Uranus Family Portrait (IR)
  119. 119. Miranda <ul><li>Voyager 2 revealed Miranda’s “mixed up” surface </li></ul><ul><li>Heavily cratered areas, with weird grooves, valleys, and cliffs </li></ul><ul><li>Miranda may have been partially shattered and reassembled </li></ul><ul><li>Consists of water ice and rock, about 440 miles in diameter. </li></ul><ul><li>Miranda is the daughter of the magician Prospero in Shakespeare’s The Tempest </li></ul>
  120. 120. Miranda Views
  121. 121. Cliffs of Miranda
  122. 122. Groovy Miranda
  123. 123. Titania & Ariel
  124. 124. Transit of Uranus The HST captured a view of Ariel crossing the disk of Uranus in July 2006
  125. 125. Lore of Uranus <ul><li>Herschel : On March 13, 1781 William Herschel, while observing the sky using a six-inch reflecting telescope, discovered the planet Uranus </li></ul><ul><li>Odd appearance, it resembled a bluish disk. </li></ul><ul><li>At first Herschel thought that he had discovered a new comet. </li></ul><ul><li>Herschel observed the “comet” four days later and found that it had moved slightly. </li></ul><ul><li>This confirmed that the discovery was something in the solar system. </li></ul>
  126. 126. Herschel’s 6-inch Reflector
  127. 127. George’s Star <ul><li>In November 1781, the German astronomer Johann Bode calculated the orbit of “Planet Herschel” and found that it lay twice as far from the sun as Saturn </li></ul><ul><li>With one discovery, Herschel doubled the size of the solar system. </li></ul><ul><li>Bode suggested the name Uranus because, in mythology, Uranus was the father of Saturn </li></ul><ul><li>Herschel wanted to name it “Georgium Sidus” after the infamous George III of England </li></ul><ul><li>“ Uranus” became the accepted name after 1850 </li></ul>
  128. 128. Neptune Data Mean Distance from Sun 2,792,400,000 miles 28.8 AU Diameter at the Equator 30,770 miles Length of “Year” (revolution around the sun) 164.79 earth years Diameter if Earth = 1 3.89 Length of “Day” 16 hr. 3 min. Mass if Earth = 1 17.3 Symbol Surface Gravity if Earth = 1 1.18
  129. 129. God of the Sea <ul><li>Neptune : In Roman mythology Neptune (Greek Poseidon) was the god of the sea. </li></ul><ul><li>Neptune was discovered in 1846 at the Berlin Observatory based upon a prediction by the French astronomer Leverrier. </li></ul><ul><li>This was the first time that a planet had been predicted to exist before its discovery. </li></ul>
  130. 130. Twin of Uranus <ul><li>Neptune is composed of gas and is very similar in size and composition to Uranus. </li></ul><ul><li>Like Uranus, Neptune also has methane in its atmosphere, which gives the planet a blue color. </li></ul>
  131. 131. Magnetic Fields <ul><li>Uranus & Neptune: </li></ul><ul><li>Magnetic fields are not centered on the planet’s cores </li></ul><ul><li>Both fields extremely tilted compared to the rotation axes </li></ul><ul><ul><li>Uranus, 59 º </li></ul></ul><ul><ul><li>Neptune, 47 º </li></ul></ul><ul><ul><li>Earth, 12 º </li></ul></ul><ul><li>With most other planets, the axes of rotation and magnetic field are fairly close </li></ul>
  132. 132. The magnetic fields of Earth, Jupiter, and Saturn nearly align with their respective rotation axes. In contrast, the magnetic and geographic poles of Uranus and Neptune differ greatly.
  133. 133. Voyager 2 <ul><li>Spacecraft : Neptune has been visited by only one spacecraft, Voyager 2 on August 25, 1989. </li></ul><ul><li>During its flyby, Voyager 2 discovered six new satellites and observed the ring structure of Neptune </li></ul><ul><li>Voyager 2 had already visited Jupiter, Saturn, and Uranus before encountering Neptune </li></ul>
  134. 134. Voyager 2 Views Detail of Neptune’s clouds Neptune & Triton
  135. 135. Like Uranus, Neptune is Surrounded by Thin, Dark Rings
  136. 136. Great Dark Spot <ul><li>Great Dark Spot : For Voyager 2, displayed an ever-changing atmosphere. Uranus was featureless </li></ul><ul><li>At the time of the Voyager 2 encounter, Neptune’s most prominent feature was the Great Dark Spot </li></ul><ul><li>About half the size of Jupiter’s Great Red Spot (about the same diameter as the earth) </li></ul><ul><li>Observations from the Hubble Space Telescope in 1994 have revealed that the Great Dark Spot has vanished! </li></ul>
  137. 137. Neptune’s Great Dark Spot
  138. 138. Moon’s of Neptune <ul><li>Neptune has seven small moons and one large moon named Triton. </li></ul><ul><li>Neptune’s moons were named after “watery” characters from Greek mythology. </li></ul><ul><li>Neptune’s’ Satellites (in order outward from Neptune) </li></ul>Naiad Larissa Thalassa Proteus Despina Triton Galatea Nereid
  139. 139. Triton <ul><li>In Greek mythology, Triton is the son of Neptune </li></ul><ul><li>Triton revolution of Neptune is retrograde </li></ul><ul><li>Triton may have formed elsewhere and was later captured by Neptune </li></ul><ul><li>Triton is about 25% water ice and 75% rock </li></ul><ul><li>Triton is probably similar to Pluto </li></ul><ul><li>Triton is about 1,700 miles in diameter </li></ul>
  140. 140. Cantaloupe World <ul><li>Surface Features : Triton has a young surface with few craters </li></ul><ul><li>Its southern hemisphere is covered with an “ice cap” of frozen nitrogen and methane. </li></ul><ul><li>Complex ridges and valleys cover Triton’s surface. </li></ul><ul><li>In the Voyager 2 images, Triton’s surface resembles the skin of a cantaloupe. </li></ul>
  141. 141. Triton (V2) Triton
  142. 142. Ice Volcanoes <ul><li>Voyager images of Triton reveal “ice volcanoes” </li></ul><ul><li>Eruptions of liquid nitrogen, dust, or methane compounds from beneath the surface </li></ul><ul><li>Voyager images show an actual plume rising five miles above the surface and extending over 90 miles “downwind” </li></ul><ul><li>Triton, Io, and Enceladus are the only other bodies in the solar system besides earth that display some form of volcanism </li></ul>
  143. 143. Ice Volcanoes (V2) <ul><li>Dark streaks are possible “ice volcanoes” </li></ul>
  144. 144. Lore of Neptune <ul><li>Galileo: In 1613, Galileo observed Neptune when it happened to be very near Jupiter, but he thought that it was only a star. </li></ul><ul><li>If Galileo had been the discoverer of Neptune, then the 8th planet would have been found before the 7th. </li></ul>
  145. 145. Leverrier & Adams <ul><li>Adams & Leverrier : Due to irregularities observed in the orbit of Uranus, the astronomers Adams and Leverrier predicted the existence and location of a new planet beyond Uranus </li></ul><ul><li>This new planet was discovered by Galle and d’Arrest on September 23, 1846. </li></ul><ul><li>They pointed a telescope at the predicted position and quickly located the new planet! </li></ul><ul><li>Amazing use of Newton’s laws to find a new planet! </li></ul>