The RASC Calgary Centre - The Solar System

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The Solar System The Solar System consists of the Sun and numerous other objects either orbiting the Sun or orbiting another body which orbits the Sun. The other objects belong to one of the following major categories: Planets (as of August 24, 2006 the planets are now defined to be: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) Dwarf Planets: Ceres, Pluto, Eris, Makemake, and Haumea Moons (See my FAQ page for a list of the number of moons discovered so far) Asteroids - more than 1,000,000 of these have been discovered in many groups in different places in the Solar System, but most occupy the "Asteroid Belt" between Mars and Jupiter Trans-Neptunian Objects (TNOs) - more than 1600 of these have been discovered orbiting past Neptune in the Kuiper belt. https://www.universetoday.com/145367/over-a-hundred-new-large-objects-found-in-the-kuiper-belt/ March 12, 2020. Comets - there are more than 300 "periodic comets" (those whose orbits are known to repeat) and dozens of "non-periodic comets" (those that have been observed only once) many of which come from the extremely distant Oort Cloud The Kuiper Belt and the Oort Cloud (image from NASA) The Minor Planet Centre The Small Solar-System Bodies are documented at the Minor Planet Centre of the Smithsonian Astrophysical Observatory, which provides analytical data on these as well as the following 3 amazing diagrams showing the distribution and location of these objects: Plot of the Innermost Solar System (out to Mars) Plot of the Inner Solar System (out to Jupiter) Plot of the Outer Solar System (Jupiter and beyond) The Largest Bodies in the Solar System The following table lists all the other objects with a diameter greater than 2000 km in order of decreasing size: Data as of April 2, 2015 from NASA: Planets Fact Sheet Jovian Satellite Fact Sheet Saturnian Satellite Fact Sheet Neptunian Satellite Fact Sheet Solar System Small Worlds Fact Sheet Near Earth Object Fact Sheet JPL Solar System Bodies and Wikipedia - The Solar System Object Parent Body Diameter (Km) Previous value(s) Jupiter Sun 142984 (Equatorial) 133708 (Polar) Saturn Sun 120536 (Equatorial) 108728 (Polar) Uranus Sun 51118 (Equatorial) 49946 (Polar) Neptune Sun 49528 (Equatorial) 48682 (Polar) Earth Sun 12756.2 (Equatorial) 12713.6 (Polar) Venus Sun 12103.6 Mars Sun 6792.4 (Equatorial) 6752.4 (Polar) Ganymede Jupiter 5262.4 5268.2 Titan Saturn 5150 5151 Mercury Sun 4879.4 Callisto Jupiter 4820.6 Io Jupiter 3643.2 3642.6 The Moon Earth 3476.28 (Equatorial) 3471.94 (Polar) Europa Jupiter 3121.6 3138 Triton Neptune 2706.8 2705.2 Pluto Sun 2374 (New Horizons mission, July 13, 2015) 2306, 2329 Eris Sun 2326 The Relative Sizes of the Largest Solar System Objects - in the order above (to scale): (click the images for larger versions)    Image Credits: individual object images - I.A.U. and NASA, concept and layout - Larry McNish. Image processing and compositing - Chris McNish 2008/12/12. Here's a comparison of the Saturn system to Jupiter and the Earth-Moon system And here's a comparison of Jupiter, its rings and 4 largest moons to the Earth-Moon system and the Juno spacecraft's orbit. Also see: http://www.rense.com/general72/size.htm for a comparison between the Earth and other planets and the Sun and other stars. The Small Solar-System Bodies (updated to July 13, 2015) As noted above, there are hundreds of thousands of small bodies in the Solar System. The following table lists a selection of notable objects with a diameter less than 2500 km in order of decreasing size and none that are smaller than Diemos - the smallest Moon of Mars. The list includes: the 2 moons of Mars 12 of the 67 moons of Jupiter 23 of the 62 moons of Saturn the 27 moons of Uranus 13 of the 14 moons of Neptune the 5 moons of Pluto the 1 moon of Eris the 2 moons of Haumea the 1 moon of Quaoar the 1 moon of Orcus the 1 moon of Salacia The table includes only the largest 25 (up from 18) asteroids (with diameters greater than 200 km) of the 400,000 known Asteroids (items beginning with a 1 to 3 digit number) from Wikipedia. The table includes the 5 classified Dwarf Planets [DP] Ceres, Pluto, Eris, Haumea, and Makemake (and their moons). The table also includes 22 other Probable Dwarf Planets [pDP] (with diameters greater than 600 km). (There are over one hundred other Dwarf Planet candidates.) The table now also includes the two largest Near Earth Asteroids [NEO] - 1036 Ganymed and 433 Eros. The table does not list any comets since the size of the coma is usually much larger than the nucleus and changes with distance from the Sun. (Data from NASA and Wikipedia.) Mike Brown, Professor of Planetary Astronomy at Caltech who discovered Eris and 15 other TNOs, keeps a list of Dwarf Planets at: http://www.gps.caltech.edu/~mbrown/dps.html Object Parent Body Diameter (Km) Pluto [DP] Sun 2374 Eris [DP] Sun 2326 Titania Uranus 1576.8 Gonggong (2007OR10) [pDP] Sun 1535 Rhea Saturn 1527.6 Oberon Uranus 1522.8 Iapetus Saturn 1469 Makemake [DP] Sun 1430 Haumea [DP] Sun 1540 Charon Pluto 1212 Umbriel Uranus 1169.4 Ariel Uranus 1157.8 Dione Saturn 1122.8 Quaoar [pDP] Sun 1110 Tethys Saturn 1062 Sedna [pDP] Sun 995 Ceres [DP] Sun 946 Mani (2002MS4) [pDP] Sun 934 Orcus [pDP] Sun 917 Salacia [pDP] Sun 854 Varuna [pDP] Sun 767 2013FY27 [pDP] Sun 763 2003AZ84 [pDP] Sun 747 2002UX25 [pDP] Sun 704 2004GV9 [pDP] Sun 703 2002AW197 [pDP] Sun 701 2005RN43 [pDP] Sun 697 2005UQ513 [pDP] Sun 693 Varda [pDP] Sun 693 Dysnomia Eris 684 Ixion [pDP] Sun 674 2007JJ43 [pDP] Sun 616 2007UK126 [pDP] Sun 612 Chaos [pDP] Sun 612 2010KZ39 [pDP] Sun 601 2012VP113 [pDP] Sun 601 2013FZ27 [pDP] Sun 601 2 Pallas Sun 544 4 Vesta Sun 525.4 Enceladus Saturn 504.2 Miranda Uranus 471.6 10 Hygiea Sun 431 Proteus Neptune 420 Mimas Saturn 396.4 Nereid Neptune 340 704 Interamnia Sun 326 Hi'iaka Haumea 320 52 Europa Sun 315 Actaea Salacia 303 511 Davida Sun 289 87 Sylvia Sun 286 Vanth Orcus 276 65 Cybele Sun 273 Hyperion Saturn 270 15 Eunomia Sun 268 3 Juno Sun 258 31 Euphrosyne Sun 256 624 Hektor Sun 241 88 Thisbe Sun 232 324 Bamberga Sun 229 451 Patientia Sun 225 48 Doris Sun 222 532 Herculina Sun 222 375 Ursula Sun 216 107 Camilla Sun 215 45 Eugenia Sun 213 7 Iris Sun 213 Phoebe Saturn 213 29 Amphitrite Sun 212 MK2 Makemake 210 423 Diotima Sun 209 19 Fortuna Sun 208 13 Egeria Sun 206 Larissa Neptune 194 Janus Saturn 179 Galatea Neptune 176 Himalia Jupiter 170 Namaka Haumea 170 Amalthea Jupiter 166.9 Puck Uranus 162 Despina Neptune 150 Sycorax Uranus 150 Portia Uranus 135 Epimetheus Saturn 116.2 Thebe Jupiter 98.6 Juliet Uranus 94 Belinda Uranus 90 Prometheus Saturn 86.2 Elara Jupiter 86 Thalassa Neptune 82 Pandora Saturn 81.4 Cressida Uranus 80 Weywot Quaoar 80 Caliban Uranus 72 Rosalind Uranus 72 Naiad Neptune 66 Desdemona Uranus 64 Halimede Neptune 62 Neso Neptune 60 Pasiphae Jupiter 60 Bianca Uranus 51 Prospero Uranus 50 Setebos Uranus 48 Carme Jupiter 46 Hydra Pluto 45 Sao Neptune 44 Metis Jupiter 43 Ophelia Uranus 43 Laomedeia Neptune 42 Cordelia Uranus 40 Psamathe Neptune 40 Siarnaq Saturn 40 Sinope Jupiter 38 Lysithea Jupiter 36 Helene Saturn 35.2 Nix Pluto 35 Kerberos (P4) Pluto 35 1036 Ganymed [NEO] Sun 32 Albiorix Saturn 32 Stephano Uranus 32 Atlas Saturn 30.2 Perdita Uranus 30 Pan Saturn 28.2 Ananke Jupiter 28 Mab Uranus 25 Telesto Saturn 24.8 Phobos Mars 22.2 Francisco Uranus 22 Paaliaq Saturn 22 Calypso Saturn 21.4 Ferdinand Uranus 20 Margaret Uranus 20 Cupid Uranus 18 S/2004 N 1 Neptune 18 Styx (P5) Pluto 18 Trinculo Uranus 18 Ymir Saturn 18 Adrastea Jupiter 16.4 Kiviuq Saturn 16 Leda Jupiter 16 Tarvos Saturn 15 433 Eros [NEO] Sun 13 Deimos Mars 12.6 The Relative Sizes of the Small Solar-System Bodies - in the order above (to scale): (Click for a larger image.) Actual photos of Pluto, Charon, Hydra and Nix, and artistic impressions of the other Largest Known Trans-Neptunian Objects (TNOs). (Click the image to see a larger version.) IAU Resolution: Definition of a Planet in the Solar System 24 August 2006, Prague 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. RESOLUTION 5A The IAU therefore resolves that "planets" and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way: (1) A "planet" 1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity 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-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape 2, (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. IAU Resolution: Pluto RESOLUTION 6A 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 objects. Return to main page