DOCSLIB.ORG

The Moons of Saturn, Uranus and Neptune

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Moons of Saturn, Uranus and Neptune Today in Astronomy 111: the moons of Saturn, Uranus and Neptune Names General features: structure, composition, orbits, origins Special moons: • Mimas • Titan • Enceladus • Iapetus • Miranda • Triton No, it’s not a sponge, or a coral, but Hyperion (Saturn VII), seen from Cassini (JPL/NASA). 15 November 2011 Astronomy 111, Fall 2011 1 Lunar nomenclature As we’ve mentioned, Jupiter’s moons are named after the mythological girlfriends and boyfriends of Zeus, but are given their Greek, rather than Latin, names. • This tradition was started by Simon Mayer, who discovered the first four moons independently of Galileo but a few days later. Saturn’s moons are named after other Titans: the giant Greek deities of Saturn’s generation, who were displaced by the ones in Zeus’s generation. • Saturn (= Kronos) was Jupiter’s (= Zeus’s) father. • John Herschel’s names from the mid-1800s have stuck. John was the son of William Herschel, who among many other things discovered Mimas and Enceladus. 15 November 2011 Astronomy 111, Fall 2011 2 Lunar nomenclature (continued) • Soon after the Voyager missions, we ran out of Greek Titans. Since then, giants from Norse, Celtic and Inuit mythology have served for new discoveries. Uranus’s moons are named after characters in Shakespeare’s comedies, with the exception of Umbriel and Belinda, magical characters in Pope’s The Rape of the Lock. Nobody knows for sure why this theme was picked. • John Herschel was responsible for this, too; also dates from the mid-1800s. • Uranus (same in Greek and Latin) was the father of Saturn/Kronos. Johannes Bode named the planet, after discoverer William Herschel tried unsuccessfully to get it named after King George III. 15 November 2011 Astronomy 111, Fall 2011 3 Lunar nomenclature (continued) Neptune’s moons are named after children or attendants of Poseidon, again in Greek. • The tradition was begun by Camille Flammarion in the late 1800s. • William Lassell discovered, but did not name, Triton, about two weeks after the planet was discovered. He also claimed erroneously to have seen a ring. • Johann Galle, the discoverer of Neptune, tried to get the planet named after LeVerrier, who had correctly predicted its position. Cooler heads in the French Academy prevailed, and instead chose the theme of Zeus’s brother and second-in-command. See here for more details of Solar system names. 15 November 2011 Astronomy 111, Fall 2011 4 General features of the outer-planet satellites There are lots of them: currently Saturn is known to have 62 (not counting Cassini), Uranus 27, and Neptune 13, of which 8, 5 and 0 are considered Major or regular, the rest Lesser or irregular. The regular satellites are all very icy, and only the most massive are likely to be differentiated. Almost all of their densities are below those of the Galilean moons. The regular satellites are in low-eccentricity, low- inclination, prograde orbits, and rotate synchronously with their revolution. • Thus probably formed with the host planet. Inner, irregular satellites tend to be closely associated with the rings, and tend to be similar in composition to the rings (very icy in Saturn, not quite so icy in the others). 15 November 2011 Astronomy 111, Fall 2011 5 General features of the outer-planet satellites (continued) Outer, lesser satellites are all small, and tend to be substantially darker (less surface ice) than the regulars or inner-lessers. Outer-lessers also tend to have eccentric, highly inclined orbits, as often retrograde as prograde. • Thus probably captured asteroids, comets, or Kuiper- belt objects, formed elsewhere, as at Jupiter. Strong mean-motion resonances among the orbits are fairly common. But… with one possible exception, none of the moons locked in orbital resonances are both large enough and close enough to their planets for tidal heating to be as important as it is for Io and Europa. 15 November 2011 Astronomy 111, Fall 2011 6 The “regular” satellites of Saturn, Uranus and Neptune Mean Visual Semimajor axis Period Inclination Mass Radius density geometric (days) (degrees) Eccentricity (1023 gm) (105 cm) (108 cm) (Planet radii) (gm cm-3) albedo Mimas (SI) 0.375 209x196x191 1.14 0.5 185.52 3.0783 0.942422 1.53 0.0202 Enceladus (SII) 1.08 256x247x245 1.61 1 238.02 3.9494 1.370218 0.00 0.0045 Tethys (SIII) 6.27 536x528x526 1.00 0.9 294.66 4.8892 1.887802 1.86 0.0000 Dione (SIV) 11.0 560 1.50 0.7 377.40 6.2620 2.736915 0.02 0.0022 Rhea (SV) 23.1 764 1.24 0.7 527.04 8.7449 4.517500 0.35 0.0010 Titan (SVI) 1345.50 2,575 1.88 0.22 1221.83 20.2730 15.945421 0.33 0.0292 Hyperion (SVII) 0.2 185x140x113 0.50 0.3 1481.10 24.5750 21.276609 0.43 0.1042 Iapetus (SVIII) 15.9 718 1.02 0.05/0.5 3561.30 59.0910 79.330183 14.72 0.0283 Porous! Miranda (UV) 0.66 240x234.2x232.9 1.20 0.27 129.39 5.0780 1.413479 4.22 0.0027 Ariel (UI) 13.5 581.1x577.9x577.7 1.67 0.35 191.02 7.4810 2.520379 0.31 0.0034 Umbriel (UII) 11.7 584.7 1.40 0.19 266.30 10.4100 4.144177 0.36 0.0050 Titania (UIII) 35.2 788.9 1.71 0.28 435.91 17.0500 8.705872 0.14 0.0022 Oberon (UIV) 30.1 761.4 1.63 0.25 583.52 22.7900 13.463239 0.10 0.0008 Triton (NI) 214.0 1,353.40 2.05 0.76 354.76 14.3280 -5.876854 157.35 0.000016 (!!) Retrograde -22.65 (!!) so it’s not really regular. This information comes mostly from the NSSDC Fact Sheets for the Saturnian, Uranian and Neptunian satellites. 15 November 2011 Astronomy 111, Fall 2011 7 Saturn’s satellites and rings /JPL/NASA Cassini 15 November 2011 Astronomy 111, Fall 2011 8 Special moons: Mimas Mimas, at the inner edge of the E ring, is involved in many important orbital resonances. Notably with the rings (e.g. the Cassini division). Its most famous feature is the gigantic crater Herschel. The impact that created Herschel must have come close to destroying the moon. (Note the central peak.) Cassini/JPL/NASA 15 November 2011 Astronomy 111, Fall 2011 9 Special moons: Mimas (continued) Even apart from Herschel, Mimas is much more heavily cratered than is usual in the Saturnian system; similar to Iapetus and Hyperion in this regard. Why it is not heated sufficiently to be resurfaced like Io or Europa is a mystery. Flying over Mimas (Cassini/JPL/NASA) 15 November 2011 Astronomy 111, Fall 2011 10 Special moons: Titan Titan is the second largest satellite in the Solar system (slightly smaller than Ganymede), and the first one discovered after the Galilean satellites (by Huygens in 1665). It is unusual in many respects: It is the only moon in the solar system with a dense atmosphere: pressure about 1.6 Earth atmospheres at the surface, 95% nitrogen (most of the rest is ammonia), and so heavily laden with photochemical smog that the surface can’t be seen at visible wavelengths. 15 November 2011 Astronomy 111, Fall 2011 11 Special moons: Titan (continued) Los Angeles Haze in Titan’s upper atmosphere, and photochemical smog below (Cassini/ JPL/ NASA). 15 November 2011 Astronomy 111, Fall 2011 12 Special moons: Titan (continued) There are few impact craters apparent (in infrared and radar images) on the surface of Titan, and evidence of cryovolcanism, involving molten ices instead of molten rock. One of Titan’s volcanoes (Cassini/JPL/NASA) 15 November 2011 Astronomy 111, Fall 2011 13 Special moons: Titan (continued) Titan is the only Solar- system body besides Earth to have liquids permanently resident on its surface. Several lakes are seen Ontario near the poles: they Lacus change in depth over time, and are fed by rivers with deltas. In one of them – Ontario Lacus, near the south Clouds pole, liquid ethane (T = South pole 90-184 K) has been positively identified. The hydrocarbon lake (Cassini/JPL/NASA) 15 November 2011 Astronomy 111, Fall 2011 14 Special moons: Titan (continued) Radar image of Ontario Lacus, taken in 2010 by Cassini. Note the rivers. I River deltas suppose one of them should be called River “Niagara amnis.” Cassini/JPL/NASA 15 November 2011 Astronomy 111, Fall 2011 15 Special moons: Titan (continued) Ontario Lacus (left) and Lake Ontario (right), shown on the same scale. 15 November 2011 Astronomy 111, Fall 2011 16 Special moons: Titan (continued) Titan’s North-Polar Great Lake (Cassini/ JPL/NASA), left, and its northern lobe on the same scale as Lake Superior, above. 15 November 2011 Astronomy 111, Fall 2011 17 Special moons: Titan (continued) And we have visited the surface: Cassini dropped a lander (named Huygens), which safely penetrated the atmosphere, landed softly, and continued to send back images for hours before it finally froze. View from Huygens after landing (ESA/ISA/NASA). The bigger rocks in the foreground are about six inches across. 15 November 2011 Astronomy 111, Fall 2011 18 Special moons: Enceladus Enceladus has the highest albedo in the Solar system, very close to 1. So it must be covered in clean (water) ice, with a smooth surface. Indeed, the surface is smooth: not many impact craters, lots of thin cracks and fissures. At close range it displays a “pack ice”-like appearance. 15 November 2011 Astronomy 111, Fall 2011 19 Special moons: Enceladus (continued) So the surface of Enceladus is very young.
Load more

Recommended publications
  • GAME of MOONS a TALE of ICE and FIRE 3 × 50 Min
    © NASA SCIENCE GAME OF MOONS A TALE OF ICE AND FIRE 3 × 50 min. Written and produced by Ivo Filatsch 4K, 5.1 and Stereo Executive Producer: Sabine Holzer Join us on a spectacular rollercoaster ride through our solar system! This three-part series explores alien worlds of extremes right in our celestial neighbourhood, each single one amazing, fascinating, and unique in its own way. veryone knows the moon — our Moon … case for Triton. It circles around Neptune in the It may come as a surprise, but there are opposite direction — in a retrograde orbit. more than 200 of these natural satellites But this brings a problem: the laws of physics orbiting other planets in the solar system! dictate that in this situation, Triton is being EAll these moons are incredibly different regarding slowed down all the while, this way getting ever their size, but also in terms of their environments. closer to Neptune. Studying these alien worlds in detail is important. Scientists have calculated that in about 100 Thanks to the insights scientists are getting million years from now, Triton will reach its Roche through observations, measurements, and radius. This is the zone where the gravitational conclusions, we all get a better understanding of forces of Neptune will become too strong to our world as a whole. withstand — and Triton will be ripped apart into pieces … And the better we understand our neighbour- hood, the better we get to know our home planet CHAPTER 2: LIFE … Our moon is much more than just a nice decora- tion in the night sky.
    [Show full text]
  • The Solar System What’S in Our Solar System?
    The Solar System What’s in Our Solar System? • Our Solar System consists of a central star (the Sun), the eight planets orbiting the sun, several dwarf planets, moons, asteroids, comets, meteors, interplanetary gas, dust, and all the “space” in between them. • Solar System: a star (sun) together with all the objects revolving around it (planets and their moons, asteroids, comets, and so on). What’s in Our Solar System? • The word solar comes from the Latin solaris, meaning “of the sun.” Sol is the Latin word for “sun.” • The eight planets of the Solar System are named for Greek and Roman Gods and Goddesses. Planetary System Planetary System: a planet with its moon(s), • The Earth and moon are a planetary system. • The word planet comes from a Greek word meaning “wandering.” To the ancients, the five visible planets to the naked eye appeared to move, unlike the other fixed stars that were “fixed.” • Orbit: the path followed by a planet, asteroid, or comet around a star, or a moon around a planet. The word comes from the Latin orbita, meaning a “wheel track.” Planets, Dwarf Planets, Moons, Asteroids, and Comets • Planet: a large body, spherical because of its own gravity, orbiting a star and not sharing its orbit with any other large bodies. • Dwarf Planet: a planet-like body that orbits the sun and does not clear its orbital zone of other massive bodies, and is not a moon. • Moon: object revolving around a planet. The word moon is from an ancient German root meaning “moon” or “month.” Planets, Dwarf Planets, Moons, Asteroids, and Comets • Asteroid: a rocky or metallic object a few feet or a few miles in dimeter.
    [Show full text]
  • A Wunda-Full World? Carbon Dioxide Ice Deposits on Umbriel and Other Uranian Moons
    Icarus 290 (2017) 1–13 Contents lists available at ScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus A Wunda-full world? Carbon dioxide ice deposits on Umbriel and other Uranian moons ∗ Michael M. Sori , Jonathan Bapst, Ali M. Bramson, Shane Byrne, Margaret E. Landis Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA a r t i c l e i n f o a b s t r a c t Article history: Carbon dioxide has been detected on the trailing hemispheres of several Uranian satellites, but the exact Received 22 June 2016 nature and distribution of the molecules remain unknown. One such satellite, Umbriel, has a prominent Revised 28 January 2017 high albedo annulus-shaped feature within the 131-km-diameter impact crater Wunda. We hypothesize Accepted 28 February 2017 that this feature is a solid deposit of CO ice. We combine thermal and ballistic transport modeling to Available online 2 March 2017 2 study the evolution of CO 2 molecules on the surface of Umbriel, a high-obliquity ( ∼98 °) body. Consid- ering processes such as sublimation and Jeans escape, we find that CO 2 ice migrates to low latitudes on geologically short (100s–1000 s of years) timescales. Crater morphology and location create a local cold trap inside Wunda, and the slopes of crater walls and a central peak explain the deposit’s annular shape. The high albedo and thermal inertia of CO 2 ice relative to regolith allows deposits 15-m-thick or greater to be stable over the age of the solar system.
    [Show full text]
  • L RES~ARCH Coljncll ·
    NA~IOf\i'At ACADEMIES OF SCIENCE AND ENGiNEERING 7 ·.· ·.·. : NATIONAL RES~ARCH ColJNCll · of the UNITED STATES OF AMERICA UNITED• STATES NATIONAL COMMITTEEI . International Union of Radio Sden<:e Nationa.1 Radio Science Meeting 13-15 January 1982 · f l··.. ·· Sponsored by USNC/URSI in cooperation with r Institute of Electrical and Electronics Engineers University of· Colorado Boulder, Colorado U.S.A. ~· 1' National Radio Science Meeting 13-15 January 19 82 Condensed Technical Program TUESDAY, 12 JANUARY 0900 CCIR U.S. Study Group 5 OT 8-8 CCIR U.S. Study ,Gr.oup 6 Radio Building 2000-2400 USNC/URSI Meeting Broker Inn WEDNESDAY, 13 JANUARY 0900-1200 A-1 Time Domai~ 1-ieasurements CRl-42 B-1 Scattering CR2-28 B-2 Electromagnetic Theory CR2-28 C-1 Topics in Information Theory CR0-30 F-1 Propagation Theory and Models CR2-26 J-1 Millimeter-Wave Astronomy UMC Ballroom 1330-1700 A-2 Microwave/Millimeter Wave Measurements CRl-42 B-3 Antenna Theory and Practice CR2-28 B-4 Inverse Scattering CR2-6 C-2 Digital HF: Equaltz ation and Reiated CR0-30 Techniques E-1 EM Noise in the Sea CRl-40 F-2 Ground-Based Remote Sensing CR2-26 H-1 VLF-ELF Wave Injection Into the CRl-46 Magnetosphere J-2 Very Long Baseline Interferometry UMC 157 1700 Commission A Business Meeting CRl-42 Commission C Business Meeting CR0-30 Commission E Business Meeting CRl-40 Commission F Business Meeting CR2-26 Commission H Business Meeting CRl-46 1800-2000 Reception Engineering Center 2000-2200 IEEE Wave Propagation Standards Committee CRl-46 TH.URSDAY, 14 JANUARY 0830-1200 A-3
    [Show full text]
  • Pluto, Titan, and Triton: How Do Their Haze Properties Compare? B. J. Buratti1, J
    51st Lunar and Planetary Science Conference (2020) 1168.pdf Pluto, Titan, and Triton: How do their Haze Properties Compare? B. J. Buratti1, J. D. Hillier2, J. D. Hofgart- ner2, M. D. Hicks1, 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109; bon- [email protected]; 2Grays Harbor College, Aberdeen, WA 98520. Introduction: The July 2015 encounter of the New Horizons spacecraft with Pluto brought a large Kuiper Belt Object into sharp focus for the first time [1]. In- struments on the spacecraft observed Pluto at solar phase angles not visible from the Earth, where the max- imum solar phase angle is about 2°. The large solar phase angles (>150°), are especially useful for charac- terizing the properties of Pluto’s haze. But key obser- vations were not made during the encounter because of the fast nature of the flyby. These included the small solar phase angles observable from Earth. Thus, the best data set is one consisting of both spacecraft and ground-based data. We have combined Earth-based observations, in- cluding those from the Palomar Adaptive Optics (AO) system, to construct a complete solar phase curve of Figure 1: Charon and Pluto from the Palomar Pluto. Using the classical radiative transfer model of adaptive optics system. Chandrasekhar’s “Planetary Problem” (2,3) we have fit Data from the spacecraft are summarized in Table physical parameters to the surface and haze of Pluto. 2. Comparison with the properties of Titan’s haze shows Table 1- New Horizons Data used in this Study. that both worlds are factories for producing reddish, organic rich molecules.
    [Show full text]
  • The Subsurface Habitability of Small, Icy Exomoons J
    A&A 636, A50 (2020) Astronomy https://doi.org/10.1051/0004-6361/201937035 & © ESO 2020 Astrophysics The subsurface habitability of small, icy exomoons J. N. K. Y. Tjoa1,?, M. Mueller1,2,3, and F. F. S. van der Tak1,2 1 Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands e-mail: [email protected] 2 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands 3 Leiden Observatory, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands Received 1 November 2019 / Accepted 8 March 2020 ABSTRACT Context. Assuming our Solar System as typical, exomoons may outnumber exoplanets. If their habitability fraction is similar, they would thus constitute the largest portion of habitable real estate in the Universe. Icy moons in our Solar System, such as Europa and Enceladus, have already been shown to possess liquid water, a prerequisite for life on Earth. Aims. We intend to investigate under what thermal and orbital circumstances small, icy moons may sustain subsurface oceans and thus be “subsurface habitable”. We pay specific attention to tidal heating, which may keep a moon liquid far beyond the conservative habitable zone. Methods. We made use of a phenomenological approach to tidal heating. We computed the orbit averaged flux from both stellar and planetary (both thermal and reflected stellar) illumination. We then calculated subsurface temperatures depending on illumination and thermal conduction to the surface through the ice shell and an insulating layer of regolith. We adopted a conduction only model, ignoring volcanism and ice shell convection as an outlet for internal heat.
    [Show full text]
  • Apollonius of Rhodes Argonautica Book 3, Translated by Robert Cooper Seaton, Harvard University Press, Cambridge MA, 1912
    Apollonius of Rhodes Argonautica book 3, translated by Robert Cooper Seaton, Harvard University Press, Cambridge MA, 1912. (http://oaks.nvg.org/sa4ra16.html#tres) Come Now, Erato, stand by my side, and say next how Jason brought back the fleece to Iolcus aided by the love of Medea. For you share the power of Cypris, and by your love-cares charm unwedded maidens; wherefore to you too is attached a name that tells of love. Thus the heroes, unobserved, were waiting in ambush amid the thick reed-beds; but Hera and Athena took note of them, and, apart from Zeus and the other immortals, entered a chamber and took counsel together; and Hera first made trial of Athena: "Do you now first, daughter of Zeus, give advice. What must be done? Will you devise some scheme whereby they may seize the golden fleece of Aeetes and bear it to Hellas, or can they deceive the king with soft words and so work persuasion? Of a truth he is terribly overweening. Still it is right to shrink from no endeavour." Thus she spoke, and at once Athena addressed her: "I too was pondering such thoughts in my heart, Hera, when you did ask me outright. But not yet do I think that I have conceived a scheme to aid the courage of the heroes, though I have balanced many plans." She ended, and the goddesses fixed their eyes on the ground at their feet, brooding apart; and straightway Hera was the first to speak her thought: "Come, let us go to Cypris; let both of us accost her and urge her to bid her son (if only he will obey) speed his shaft at the daughter of Aeetes, the enchantress, and charm her with love for Jason.
    [Show full text]
  • Planets of the Solar System Information
    Planets of the Solar System Mercury Mercury is the smallest planet and the closest to the Sun. It travels very fast at a speed of 180 000 km/h in an elliptical orbit around the Sun. One orbit takes just 88 days. Mercury has the most eccentric orbit of all the planets, therefore its nearness to the Sun is variable. It can be as close as 47 million km and as far as 70 million km away, but is at an average distance of 57 910 000 km away from the Sun. With a diameter of 4 800km, Mercury is about 38% of the size of the Earth. Even though it is revolving very quickly around the sun it is rotating very slowly on its axis. One day on Mercury takes 59 Earth days. In the time it takes to complete two orbits Mercury only rotates three times! Average temperatures on Mercury reach 427°C Where did Mercury get its name? during the day and -173°C during the night. Mercury has no atmosphere to trap and store heat Mercury is named after the mythical Roman so it is very cold on the side of the planet that is Messenger of the Gods. He is often depicted facing away from the Sun. in art wearing winged sandles and a winged helmet. He was known for his speed. Venus Venus is the second closest planet at approximately 108 200 000 km away from the Sun. It is often referred to as our ‘sister planet’ because it has some similarities with Earth: It has a rocky surface dominated by volcanoes.
    [Show full text]
  • Lecture 12 the Rings and Moons of the Outer Planets October 15, 2018
    Lecture 12 The Rings and Moons of the Outer Planets October 15, 2018 1 2 Rings of Outer Planets • Rings are not solid but are fragments of material – Saturn: Ice and ice-coated rock (bright) – Others: Dusty ice, rocky material (dark) • Very thin – Saturn rings ~0.05 km thick! • Rings can have many gaps due to small satellites – Saturn and Uranus 3 Rings of Jupiter •Very thin and made of small, dark particles. 4 Rings of Saturn Flash movie 5 Saturn’s Rings Ring structure in natural color, photographed by Cassini probe July 23, 2004. Click on image for Astronomy Picture of the Day site, or here for JPL information 6 Saturn’s Rings (false color) Photo taken by Voyager 2 on August 17, 1981. Click on image for more information 7 Saturn’s Ring System (Cassini) Mars Mimas Janus Venus Prometheus A B C D F G E Pandora Enceladus Epimetheus Earth Tethys Moon Wikipedia image with annotations On July 19, 2013, in an event celebrated the world over, NASA's Cassini spacecraft slipped into Saturn's shadow and turned to image the planet, seven of its moons, its inner rings -- and, in the background, our home planet, Earth. 8 Newly Discovered Saturnian Ring • Nearly invisible ring in the plane of the moon Pheobe’s orbit, tilted 27° from Saturn’s equatorial plane • Discovered by the infrared Spitzer Space Telescope and announced 6 October 2009 • Extends from 128 to 207 Saturnian radii and is about 40 radii thick • Contributes to the two-tone coloring of the moon Iapetus • Click here for more info about the artist’s rendering 9 Rings of Uranus • Uranus -- rings discovered through stellar occultation – Rings block light from star as Uranus moves by.
    [Show full text]
  • Respicite Astra: a Historic Journey in Astronomy Through Books
    0 Respicite Astra: A Historic Journey in Astronomy through Books RReessppiicciittee AAssttrraa A Historic Journey in Astronomy through Books The Astronomiicall Sociiety of Mallta The Natiionall Liibrary of Mallta The Astronomical Society of Malta The National Library of Malta 1 Respicite Astra: A Historic Journey in Astronomy through Books Respicite Astra A Historic Journey in Astronomy through Books Exhibition held between 25 September – 18 October 2010-09-21 at the National Library, Valletta, Malta on the occasion of Notte Bianca 2010 Introductory Text Mr Victor Farrugia Captions Mr Leonard Ellul Mercer – Pgs 23-24, 57 Mr Alexander Pace – Pgs 25-26, 58, 63, 70 Prof Frank Ventura – Pgs 4, 6-13, 15-18, 21, 27-31, 33, 35-38, 40, 42- 43, 45-48, 50-56, 60-62, 65-69, 72-76, 80, 85, 87, 93 Acknowledgements The Committee of the Astronomical Society of Malta would like to acknowledge the following persons for their kind and generous help in setting up this Exhibition at the Main Hall of the National Library starting on 25th September 2010 during the Notte Bianca event: Mr Fabio Agius (MaltaPost Philatelic Archives) Ms C Michelle Buhagiar (National Library of Malta) Ms Maroma Camilleri National Library of Malta) Mr Leonard Ellul Mercer (Personal capacity) Victor Farrugia (Astronomical Society of Malta) Mr Alexander Pace (Astronomical Society of Malta) Arch Alexei Pace (Astronomical Society of Malta) Ms Joanne Sciberras (National Library of Malta) Mr Tony Tanti (Astronomical Society of Malta) Prof Frank Ventura (University of Malta) Staff of the National Library of Malta Front Image Great Orion Nebula by Mr Leonard Ellul Mercer Production The Astronomical Society of Malta P.O.
    [Show full text]
  • The Rings and Inner Moons of Uranus and Neptune: Recent Advances and Open Questions
    Workshop on the Study of the Ice Giant Planets (2014) 2031.pdf THE RINGS AND INNER MOONS OF URANUS AND NEPTUNE: RECENT ADVANCES AND OPEN QUESTIONS. Mark R. Showalter1, 1SETI Institute (189 Bernardo Avenue, Mountain View, CA 94043, mshowal- [email protected]! ). The legacy of the Voyager mission still dominates patterns or “modes” seem to require ongoing perturba- our knowledge of the Uranus and Neptune ring-moon tions. It has long been hypothesized that numerous systems. That legacy includes the first clear images of small, unseen ring-moons are responsible, just as the nine narrow, dense Uranian rings and of the ring- Ophelia and Cordelia “shepherd” ring ε. However, arcs of Neptune. Voyager’s cameras also first revealed none of the missing moons were seen by Voyager, sug- eleven small, inner moons at Uranus and six at Nep- gesting that they must be quite small. Furthermore, the tune. The interplay between these rings and moons absence of moons in most of the gaps of Saturn’s rings, continues to raise fundamental dynamical questions; after a decade-long search by Cassini’s cameras, sug- each moon and each ring contributes a piece of the gests that confinement mechanisms other than shep- story of how these systems formed and evolved. herding might be viable. However, the details of these Nevertheless, Earth-based observations have pro- processes are unknown. vided and continue to provide invaluable new insights The outermost µ ring of Uranus shares its orbit into the behavior of these systems. Our most detailed with the tiny moon Mab. Keck and Hubble images knowledge of the rings’ geometry has come from spanning the visual and near-infrared reveal that this Earth-based stellar occultations; one fortuitous stellar ring is distinctly blue, unlike any other ring in the solar alignment revealed the moon Larissa well before Voy- system except one—Saturn’s E ring.
    [Show full text]
  • Titan and Enceladus $1 B Mission
    JPL D-37401 B January 30, 2007 Titan and Enceladus $1B Mission Feasibility Study Report Prepared for NASA’s Planetary Science Division Prepared By: Kim Reh Contributing Authors: John Elliott Tom Spilker Ed Jorgensen John Spencer (Southwest Research Institute) Ralph Lorenz (The Johns Hopkins University, Applied Physics Laboratory) KSC GSFC ARC Approved By: _________________________________ Kim Reh Dr. Ralph Lorenz Jet Propulsion Laboratory The Johns Hopkins University, Applied Study Manager Physics Laboratory Titan Science Lead _________________________________ Dr. John Spencer Southwest Research Institute Enceladus Science Lead Pre-decisional — For Planning and Discussion Purposes Only Titan and Enceladus Feasibility Study Report Table of Contents JPL D-37401 B The following members of an Expert Advisory and Review Board contributed to ensuring the consistency and quality of the study results through a comprehensive review and advisory process and concur with the results herein. Name Title/Organization Concurrence Chief Engineer/JPL Planetary Flight Projects Gentry Lee Office Duncan MacPherson JPL Review Fellow Glen Fountain NH Project Manager/JHU-APL John Niehoff Sr. Research Engineer/SAIC Bob Pappalardo Planetary Scientist/JPL Torrence Johnson Chief Scientist/JPL i Pre-decisional — For Planning and Discussion Purposes Only Titan and Enceladus Feasibility Study Report Table of Contents JPL D-37401 B This page intentionally left blank ii Pre-decisional — For Planning and Discussion Purposes Only Titan and Enceladus Feasibility Study Report Table of Contents JPL D-37401 B Table of Contents 1. EXECUTIVE SUMMARY.................................................................................................. 1-1 1.1 Study Objectives and Guidelines............................................................................ 1-1 1.2 Relation to Cassini-Huygens, New Horizons and Juno.......................................... 1-1 1.3 Technical Approach...............................................................................................
    [Show full text]