Data Planet Tata Surya
PLANETARY DATA
Compiled by
IRFAN ANSHORY
MERCURY
Mean distance from Sun: 57.9 million km
Equatorial diameter: 4,880 km
Period of revolution: 88 days
Period of rotation: 58.6 days
Mass (relative to Earth): 0.055
Surface gravity: 3.70 m/s2
Escape velocity: 4.3 km/s
Speed in orbit: 24 km/s
Mean surface temperature: 170 celcius
Density: 5.41 gram/cm3
Inclination of axis: 0.1
Inclination of orbit to ecliptic: 7
Eccentricity of orbit: 0.206
Atmosphere: None
Satellites: 0
Rings: 0
V E N U S
Mean distance from Sun: 108.2 million km
Equatorial diameter: 12,104 km
Period of revolution: 224.7 days
Period of rotation: 243 days, retrograde
Mass (relative to Earth): 0.815
Surface gravity: 8.87 m/s2
Escape velocity: 10.36 km/s
Speed in orbit: 35 km/s
Mean surface temperature: 470 celcius
Density: 5.25 gram/cm3
Inclination of axis: 3
Inclination of orbit to ecliptic: 3.4
Eccentricity of orbit: 0.007
Atmosphere: 96% CO2; 3.5% N2; 0.4% Ar; 0.05% O2
Satellites: 0
Rings: 0
E A R T H
Mean distance from Sun: 149.6 million km
Equatorial diameter: 12,756 km
Period of revolution: 365.25 days
Period of rotation: 23 h, 56 m, 4 s
Mass: 6.0 x 1024 kg
Surface gravity: 9.78 m/s2
Escape velocity: 11.18 km/s
Speed in orbit: 29.78 km/s
Mean surface temperature: 20 celcius
Density: 5.52 gram/cm3
Inclination of axis: 23 27’
Inclination of orbit to ecliptic: 0
Eccentricity of orbit: 0.017
Atmosphere: 78% N2; 21% O2; 0.93% Ar; 0.03% CO2
Satellites: 1
Rings: 0
M A R S
Mean distance from Sun: 227.9 million km
Equatorial diameter: 6,794 km
Period of revolution: 687 days
Period of rotation: 24 h, 37 m
Mass (relative to Earth): 0.107
Surface gravity: 3.70 m/s2
Escape velocity: 5 km/s
Speed in orbit: 24 km/s
Mean surface temperature: -65 celcius
Density: 3.90 gram/cm3
Inclination of axis: 25 12’
Inclination of orbit to ecliptic: 1.9
Eccentricity of orbit: 0.093
Atmosphere: 95% CO2; 3% N2; 1.6% Ar; 0.2% O2
Satellites: 2
Rings: 0
JUPITER
Mean distance from Sun: 778.4 million km
Equatorial diameter: 142,984 km
Period of revolution: 11.86 years
Period of rotation: 9 h, 55 m, 30 s
Mass (relative to Earth): 317.7
Surface gravity: 23.12 m/s2
Escape velocity: 59.5 km/s
Speed in orbit: 13 km/s
Mean surface temperature: -150 celcius
Density: 1.30 gram/cm3
Inclination of axis: 3 5’
Inclination of orbit to ecliptic: 1.3
Eccentricity of orbit: 0.048
Atmosphere: 90% H2; 10% He
Satellites: 63
Rings: 3
SATURN
Mean distance from Sun: 1,427 million km
Equatorial diameter: 120,660 km
Period of revolution: 29.46 years
Period of rotation: 10 h, 40 m, 24 s
Mass (relative to Earth): 95.16
Surface gravity: 8.96 m/s2
Escape velocity: 35.5 km/s
Speed in orbit: 9.7 km/s
Mean surface temperature: -180 celcius
Density: 0.70 gram/cm3
Inclination of axis: 26 44’
Inclination of orbit to ecliptic: 2.5
Eccentricity of orbit: 0.056
Atmosphere: 97% H2; 3% He
Satellites: 56
Rings: 1000(?)
URANUS
Mean distance from Sun: 2,870 million km
Equatorial diameter: 51,810 km
Period of revolution: 84 years
Period of rotation: 17 h, retrograde
Mass (relative to Earth): 14.54
Surface gravity: 8.7 m/s2
Escape velocity: 21.3 km/s
Speed in orbit: 6.8 km/s
Mean surface temperature: -230 celcius
Density: 1.30 gram/cm3
Inclination of axis: 97 55’
Inclination of orbit to ecliptic: 0,8
Eccentricity of orbit: 0.047
Atmosphere: 83% H2; 15% He; 2% CH4
Satellites: 27
Rings: 11
NEPTUNE
Mean distance from Sun: 4,497 million km
Equatorial diameter: 49,532 km
Period of revolution: 165 years
Period of rotation: 16 h, 11 m
Mass (relative to Earth): 17.14
Surface gravity: 11 m/s2
Escape velocity: 23.5 km/s
Speed in orbit: 5.4 km/s
Mean surface temperature: -250 celcius
Density: 1.70 gram/cm3
Inclination of axis: 28 48’
Inclination of orbit to ecliptic: 1.8
Eccentricity of orbit: 0,009
Atmosphere: 74% H2; 23% He; 3% CH4
Satellites: 13
Rings: 4
P L U T O
Mean distance from Sun: 5,909 million km
Equatorial diameter: 2,290 km
Period of revolution: 248 years
Period of rotation: 6.375 days, retrograde
Mass (relative to Earth): 0.0022
Surface gravity: 0.58 m/s2
Escape velocity: 1.1 km/s
Speed in orbit: 4.7 km/s
Mean surface temperature: -280 celcius
Density: 1.99 gram/cm3
Inclination of axis: 60
Inclination of orbit to ecliptic: 17.2
Eccentricity of orbit: 0.254
Atmosphere: None
Satellites: 3
Rings: 0
HOW THE PLANETS AND SATELLITES GOT THEIR NAMES
MERCURY
Named for the winged Roman god of travel because it appears to move so swiftly.
VENUS
Roman name for the goddess of love. This planet was considered to be the brightest and most beautiful planet or star in the heavens.
EARTH
The name Earth comes from the Indo-European base 'er,' which produced the German 'erde,' Dutch 'aarde,' Danish and Swedish 'jord,' and English 'earth.' Related forms include Greek 'eraze,' meaning 'on the ground,' and Welsh 'erw,' meaning 'field.'
THE MOON: Every civilization has had a name for the satellite of Earth that is known, in English, as the Moon. The name is of Anglo-Saxon derivation.
MARS
Named by the Romans for their god of war because of its red, bloodlike color. Other civilizations also named this planet from this attribute; the Egyptians named it “Her Desher,” meaning “the red one.”
SATELLITES: Phobos (named for one of the horses that drew Mars' chariot); Deimos (named for one of Mars' companions).
JUPITER
The largest and most massive of the planets was named Zeus by the Greeks and Jupiter by the Romans; he was the most important deity in both pantheons. Jupiter's satellites are named after mythological characters who have some relationship to Zeus.
SATELLITES: Metis (first wife of Zeus); Adrastea (a nymph of Crete to whose care Zeus's mother entrusted the infant Zeus); Amalthea (a goat in some accounts, a princess of Crete in others, she suckled Zeus as a young child); Thebe (a nymph abducted by Zeus); Io (she was changed by Zeus into a cow to protect her from his jealous wife); Europa (she was seduced by Jupiter); Ganymede (beautiful young boy who became the cupbearer of the Olympian gods); Callisto (she was seduced by Zeus, who changed her into a bear to protect her from his wife's jealousy); Leda (seduced by Zeus in the form of a swan); Himalia (nymph who bore three sons of Zeus); Lysithia (one of Zeus' many lovers); Elara (a paramour of Zeus); Ananke (daughter of Zeus and Adrastea, goddess of fate and necessity); Carme (mother, by Zeus, of Britomartis); Pasiphaë (wife of Minos, mother of the Minotaur); Sinope (daughter of the river god Asopus and Merope). Other recently discovered and named satellites of Jupiter are: Themisto, Euporie, Orthosie, Euanthe, Thyone, Harpalyke, Hermippe, Praxidike, Iocaste, Passithee, Chaldene, Kale, Isonoe, Aitne, Erinome, Taygete, Kalyke, Eurydome, Autonoe, Sponde, Megaclite, and Callirrhoe. The names come from members of Jupiter's (or Zeus's) entourage. The 2003 Jovian moons were named after daughters of Zeus: Hegemone, Mneme, Aoede, Thelxinoe, Arche, Kallichore, Helike, Carpo, Eukelade, and Cyllene.
Between 2000 and 2003, 45 moons were found, bringing Jupiter's satellite total to 63, the greatest in the solar system. The new moons were generally small with distant retrograde orbits (orbital movement opposite to the planet's spin). Most of the new moons were sighted using Hawaii's Mauna Kea telescopes. Some astronomers believe that Jupiter's moon count could reach 100.
SATURN
Saturn was the Roman name for the Greek Cronos, god of farming and the father of Zeus/Jupiter. Some of its satellites were named for Titans who, according to Greek mythology, were brothers and sisters of Saturn.
SATELLITES: Pan (the half-human, half-goat god of pastoralism); Atlas (a Titan who held the heavens on his shoulders); Prometheus (a Titan who gave many gifts to humanity, including fire); Pandora (a woman who opened the box that loosed a host of plagues upon humanity); Janus (a two-faced Roman god who could look forward and backward at the same time); Epimetheus (a Greek backward-looking god); Mimas (a Titan felled by Hephaestus); Enceladus (a Titan killed by Athene); Tethys (the wife of Oceanus and mother of all rivers); Telesto (a water nymph); Calypso (a daughter of Atlas and paramour of Odysseus); Dione (a sister of Cronos); Helene (a daughter of Zeus); Rhea (a daughter of Cronos); Titan; Hyperion (a Titan); Iapetus (a Titan); Phoebe (another name for Artemis, goddess of the moon).
The newest satellites were named for Gallic (Gaul, or ancient France), Norse, and Inuit (Eskimo) giants: Kiviuq, Ijiraq, Paaliaq, Skadi, Albiorix, Erriapo, Siarnaq, Tarvos, Mundilfari, Suttung, Thrym, and Ymir.
Saturn has 56 known moons, nine of which were announced in June 2006 and are known by the temporary designations S/2004 S19 and S/2006 S1 through S8.
URANUS
Uranus was named for the Greek god of the sky. The astronmer William Lassell, who discovered two of Uranus' satellites in 1851, started the tradition of naming all of the planet's satellites for characters in the work of William Shakepseare and Alexander Pope.
SATELLITES: Cordelia (daughter of Lear in Shakespeare's “King Lear”); Ophelia (daughter of Polonius, fiance of Hamlet in Shakespeare's “Hamlet”); Bianca (daughter of Baptista, sister of Kate in Shakespeare's “Taming of the Shrew”); Cressida (title character in Shakespeare's “Troilus and Cressida”); Desdemona (wife of Othello in Shakespeare's “Othello”); Juliet (heroine of Shakespeare's “Romeo and Juliet”); Portia (rich heiress in Shakespeare's “Merchant of Venice”); Rosalind (daughter of the banished duke in Shakespeare's “As You Like It”); Belinda (character in Pope's “Rape of the Lock”); Puck (mischievous spirit in Shakespeare's “A Midsummer Night's Dream”); Miranda (the heroine of Shakespeare's “The Tempest”); Ariel (a benevolent spirit in Shakespeare's “The Tempest”); Umbriel (a malevolent spirit in Pope's“ Rape of the Lock”); Titania (the queen of the fairies in Shakespeare's “A Midsummer Night's Dream”); Oberon (the king of the fairies in “A Midsummer Night's Dream”); Caliban (the brutish slave in Shakespeare's “The Tempest”); Sycorax (Caliban's mother in “The Tempest”); Prospero (the rightful Duke of Milan in “The Tempest”); Setebos (a false god worshiped by Caliban in “The Tempest”); Stephano (a drunken butler in “The Tempest”); Trinculo (a jester in “The Tempest”).
There are 27 known moons of Uranus. Ten of the moons, being closer to the planet, have faster periods of revolution (8–15 hours) than their more distant relatives.
NEPTUNE
Neptune, a blue planet, was named for the Roman god of the sea.
SATELLITES: Naiad (a group of Greek water nymphs who were guardians of lakes, fountains, springs and rivers); Thalassa (Greek sea goddess); Despina (daughter of Neptune); Galatea (one of the attendants of Neptune); Larissa (a lover of Neptune); Proteus (a Greek sea god); Triton (the sea-god son of Poseidon/Neptune); Nereid (the Nereids, a group of fifty daughters, were attendants of Neptune).
In Jan. 2003, astronomers from the Harvard-Smithsonian Center for Astrophysics and the National Research Council of Canada announced that three new moons had been discovered orbiting Neptune. Two more moons were announced later in 2003, bringing the total to 13. Five other recently discovered satellites are still unnamed.
PLUTO
Pluto, the outermost planet in our solar system, was named after Roman god of the underworld, who was able to render himself invisible. In Aug. 2006, the International Astronomical Union (IAU) declared Pluto to be a dwarf planet.
SATELLITE: Charon (the mythological boatman who ferried souls across the river Styx to Pluto for judgement).
Two new moons were sighted by the Hubble Space Telescope in Oct. 2005 and confirmed in Feb. 2006, bringing Pluto's satellites to three.***
NEW DWARF PLANET NAMED ERIS
Discovery
In July 2005, a team from the California Institute of Technology headed by astronomer Michael Brown announced the discovery of a possible "tenth planet," which was temporarily called 2003 UB-313. This most distant object so far found in our solar system is larger than Pluto and takes 560 years to orbit the Sun. Most planets circle the Sun very near the same plane as Earth's orbit, but the new object's orbit is off this elliptic plane by about 44 degrees. Astronomers studying this object nicknamed it "Xena" and in 2006 discovered it had a moon, nicknamed "Gabrielle."
Xena's size helped spark the drive for a decisive definition of a planet. Under a proposal presented at the start of the triennial assembly of the International Astronomical Union (IAU) in 2006, the union would have added two more planets to the solar system: Xena and the asteroid Ceres.
Dwarf planet
After much debate, the union decided to classify Xena, Pluto, and Ceres as dwarf planets. Other recently found Trans-Neptunian Objects (TNOs) expected to be declared dwarf planets in this class are Varuna (2000), Ixion (2001), Quaoar (2002), Orcus (2003), and Sedna (2004).
The IAU General Assembly in Prague on August 24, 2006, reduced the solar system from nine to eight planets on the vote of less than 5% of nearly 9,000 members. The new president, Catherine Cesarsky—the first woman to head the union—will have to deal with refining the decisions made at the assembly. A number of astronomers are unhappy with the outcome of the vote and it is expected that the 2009 general assembly in Rio de Janeiro will have more to say on the subject.
New name
On September 13, 2006, the IAU announced the official name of the object formerly known as Xena. The new name, which had been submitted by Michael Brown, is Eris, the Greek goddess of strife or discord. Eris's moon is now Dysnomia, daughter of Eris.
The goddess Eris at a wedding party tossed a golden apple into the crowd of guests inscribed kallisti, or "for the prettiest." This led to an argument among the goddesses Athena, Hera, and Aphrodite over which deserved the apple. This seems appropriate for the name of a object which sparked intense debate among astronomers and the general public about the definition of a planet, leading to Pluto getting kicked out of the club amidst vocal protests.***
PLUTO DEMOTED!
(Not a planet anymore)
New Definition of a Planet
The International Astronomical Union (IAU) voted on an official definition of the word "planet" at their general assembly in Prague on Aug. 24, 2006. Celestial bodies must meet the following conditions in order to be classified as planets: (1) The object must be in orbit around a star, while not being itself a star, (2) the body must be massive enough for its own gravity to pull it into a nearly spherical shape, and (3) the object has cleared the neighborhood around its orbit. The last criterion is the one that led to Pluto's demotion. While the exact parameters of "clearing the neighborhood" have not been set, the other planets have either assimilated or repulsed most other objects in their orbits, and each has more mass than the combined total of everything else in its area. The same cannot be said for Pluto, which has turned out to be one of many objects in its orbit.
Pluto is Out!
Pluto's new classification is "dwarf planet," while the eight planets remaining—Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune—are planets. The asteroid Ceres (classified a planet when first discovered in the 1801) and Eris (previously nicknamed "Xena") have joined Pluto as dwarfs. The IAU also has a dozen candidate planets awaiting future designation as dwarf planets: Sedna (2004), Orcus (2003), Quaoar (2002), Ixion (2001), Varuna (2000)—all found beyond Pluto; the asteroids Vesta, Pallas, Hygiea; and four yet unnamed bodies (2003 EL-61; 2005 FY-9; 2002 TX-300; 2002 AW-197).
Also defined was "Small Solar System Bodies" as all other objects except satellites orbiting the Sun. These include the asteroids, Trans-Neptunian Objects, comets and other small bodies.***
Compiled by
IRFAN ANSHORY
MERCURY
Mean distance from Sun: 57.9 million km
Equatorial diameter: 4,880 km
Period of revolution: 88 days
Period of rotation: 58.6 days
Mass (relative to Earth): 0.055
Surface gravity: 3.70 m/s2
Escape velocity: 4.3 km/s
Speed in orbit: 24 km/s
Mean surface temperature: 170 celcius
Density: 5.41 gram/cm3
Inclination of axis: 0.1
Inclination of orbit to ecliptic: 7
Eccentricity of orbit: 0.206
Atmosphere: None
Satellites: 0
Rings: 0
V E N U S
Mean distance from Sun: 108.2 million km
Equatorial diameter: 12,104 km
Period of revolution: 224.7 days
Period of rotation: 243 days, retrograde
Mass (relative to Earth): 0.815
Surface gravity: 8.87 m/s2
Escape velocity: 10.36 km/s
Speed in orbit: 35 km/s
Mean surface temperature: 470 celcius
Density: 5.25 gram/cm3
Inclination of axis: 3
Inclination of orbit to ecliptic: 3.4
Eccentricity of orbit: 0.007
Atmosphere: 96% CO2; 3.5% N2; 0.4% Ar; 0.05% O2
Satellites: 0
Rings: 0
E A R T H
Mean distance from Sun: 149.6 million km
Equatorial diameter: 12,756 km
Period of revolution: 365.25 days
Period of rotation: 23 h, 56 m, 4 s
Mass: 6.0 x 1024 kg
Surface gravity: 9.78 m/s2
Escape velocity: 11.18 km/s
Speed in orbit: 29.78 km/s
Mean surface temperature: 20 celcius
Density: 5.52 gram/cm3
Inclination of axis: 23 27’
Inclination of orbit to ecliptic: 0
Eccentricity of orbit: 0.017
Atmosphere: 78% N2; 21% O2; 0.93% Ar; 0.03% CO2
Satellites: 1
Rings: 0
M A R S
Mean distance from Sun: 227.9 million km
Equatorial diameter: 6,794 km
Period of revolution: 687 days
Period of rotation: 24 h, 37 m
Mass (relative to Earth): 0.107
Surface gravity: 3.70 m/s2
Escape velocity: 5 km/s
Speed in orbit: 24 km/s
Mean surface temperature: -65 celcius
Density: 3.90 gram/cm3
Inclination of axis: 25 12’
Inclination of orbit to ecliptic: 1.9
Eccentricity of orbit: 0.093
Atmosphere: 95% CO2; 3% N2; 1.6% Ar; 0.2% O2
Satellites: 2
Rings: 0
JUPITER
Mean distance from Sun: 778.4 million km
Equatorial diameter: 142,984 km
Period of revolution: 11.86 years
Period of rotation: 9 h, 55 m, 30 s
Mass (relative to Earth): 317.7
Surface gravity: 23.12 m/s2
Escape velocity: 59.5 km/s
Speed in orbit: 13 km/s
Mean surface temperature: -150 celcius
Density: 1.30 gram/cm3
Inclination of axis: 3 5’
Inclination of orbit to ecliptic: 1.3
Eccentricity of orbit: 0.048
Atmosphere: 90% H2; 10% He
Satellites: 63
Rings: 3
SATURN
Mean distance from Sun: 1,427 million km
Equatorial diameter: 120,660 km
Period of revolution: 29.46 years
Period of rotation: 10 h, 40 m, 24 s
Mass (relative to Earth): 95.16
Surface gravity: 8.96 m/s2
Escape velocity: 35.5 km/s
Speed in orbit: 9.7 km/s
Mean surface temperature: -180 celcius
Density: 0.70 gram/cm3
Inclination of axis: 26 44’
Inclination of orbit to ecliptic: 2.5
Eccentricity of orbit: 0.056
Atmosphere: 97% H2; 3% He
Satellites: 56
Rings: 1000(?)
URANUS
Mean distance from Sun: 2,870 million km
Equatorial diameter: 51,810 km
Period of revolution: 84 years
Period of rotation: 17 h, retrograde
Mass (relative to Earth): 14.54
Surface gravity: 8.7 m/s2
Escape velocity: 21.3 km/s
Speed in orbit: 6.8 km/s
Mean surface temperature: -230 celcius
Density: 1.30 gram/cm3
Inclination of axis: 97 55’
Inclination of orbit to ecliptic: 0,8
Eccentricity of orbit: 0.047
Atmosphere: 83% H2; 15% He; 2% CH4
Satellites: 27
Rings: 11
NEPTUNE
Mean distance from Sun: 4,497 million km
Equatorial diameter: 49,532 km
Period of revolution: 165 years
Period of rotation: 16 h, 11 m
Mass (relative to Earth): 17.14
Surface gravity: 11 m/s2
Escape velocity: 23.5 km/s
Speed in orbit: 5.4 km/s
Mean surface temperature: -250 celcius
Density: 1.70 gram/cm3
Inclination of axis: 28 48’
Inclination of orbit to ecliptic: 1.8
Eccentricity of orbit: 0,009
Atmosphere: 74% H2; 23% He; 3% CH4
Satellites: 13
Rings: 4
P L U T O
Mean distance from Sun: 5,909 million km
Equatorial diameter: 2,290 km
Period of revolution: 248 years
Period of rotation: 6.375 days, retrograde
Mass (relative to Earth): 0.0022
Surface gravity: 0.58 m/s2
Escape velocity: 1.1 km/s
Speed in orbit: 4.7 km/s
Mean surface temperature: -280 celcius
Density: 1.99 gram/cm3
Inclination of axis: 60
Inclination of orbit to ecliptic: 17.2
Eccentricity of orbit: 0.254
Atmosphere: None
Satellites: 3
Rings: 0
HOW THE PLANETS AND SATELLITES GOT THEIR NAMES
MERCURY
Named for the winged Roman god of travel because it appears to move so swiftly.
VENUS
Roman name for the goddess of love. This planet was considered to be the brightest and most beautiful planet or star in the heavens.
EARTH
The name Earth comes from the Indo-European base 'er,' which produced the German 'erde,' Dutch 'aarde,' Danish and Swedish 'jord,' and English 'earth.' Related forms include Greek 'eraze,' meaning 'on the ground,' and Welsh 'erw,' meaning 'field.'
THE MOON: Every civilization has had a name for the satellite of Earth that is known, in English, as the Moon. The name is of Anglo-Saxon derivation.
MARS
Named by the Romans for their god of war because of its red, bloodlike color. Other civilizations also named this planet from this attribute; the Egyptians named it “Her Desher,” meaning “the red one.”
SATELLITES: Phobos (named for one of the horses that drew Mars' chariot); Deimos (named for one of Mars' companions).
JUPITER
The largest and most massive of the planets was named Zeus by the Greeks and Jupiter by the Romans; he was the most important deity in both pantheons. Jupiter's satellites are named after mythological characters who have some relationship to Zeus.
SATELLITES: Metis (first wife of Zeus); Adrastea (a nymph of Crete to whose care Zeus's mother entrusted the infant Zeus); Amalthea (a goat in some accounts, a princess of Crete in others, she suckled Zeus as a young child); Thebe (a nymph abducted by Zeus); Io (she was changed by Zeus into a cow to protect her from his jealous wife); Europa (she was seduced by Jupiter); Ganymede (beautiful young boy who became the cupbearer of the Olympian gods); Callisto (she was seduced by Zeus, who changed her into a bear to protect her from his wife's jealousy); Leda (seduced by Zeus in the form of a swan); Himalia (nymph who bore three sons of Zeus); Lysithia (one of Zeus' many lovers); Elara (a paramour of Zeus); Ananke (daughter of Zeus and Adrastea, goddess of fate and necessity); Carme (mother, by Zeus, of Britomartis); Pasiphaë (wife of Minos, mother of the Minotaur); Sinope (daughter of the river god Asopus and Merope). Other recently discovered and named satellites of Jupiter are: Themisto, Euporie, Orthosie, Euanthe, Thyone, Harpalyke, Hermippe, Praxidike, Iocaste, Passithee, Chaldene, Kale, Isonoe, Aitne, Erinome, Taygete, Kalyke, Eurydome, Autonoe, Sponde, Megaclite, and Callirrhoe. The names come from members of Jupiter's (or Zeus's) entourage. The 2003 Jovian moons were named after daughters of Zeus: Hegemone, Mneme, Aoede, Thelxinoe, Arche, Kallichore, Helike, Carpo, Eukelade, and Cyllene.
Between 2000 and 2003, 45 moons were found, bringing Jupiter's satellite total to 63, the greatest in the solar system. The new moons were generally small with distant retrograde orbits (orbital movement opposite to the planet's spin). Most of the new moons were sighted using Hawaii's Mauna Kea telescopes. Some astronomers believe that Jupiter's moon count could reach 100.
SATURN
Saturn was the Roman name for the Greek Cronos, god of farming and the father of Zeus/Jupiter. Some of its satellites were named for Titans who, according to Greek mythology, were brothers and sisters of Saturn.
SATELLITES: Pan (the half-human, half-goat god of pastoralism); Atlas (a Titan who held the heavens on his shoulders); Prometheus (a Titan who gave many gifts to humanity, including fire); Pandora (a woman who opened the box that loosed a host of plagues upon humanity); Janus (a two-faced Roman god who could look forward and backward at the same time); Epimetheus (a Greek backward-looking god); Mimas (a Titan felled by Hephaestus); Enceladus (a Titan killed by Athene); Tethys (the wife of Oceanus and mother of all rivers); Telesto (a water nymph); Calypso (a daughter of Atlas and paramour of Odysseus); Dione (a sister of Cronos); Helene (a daughter of Zeus); Rhea (a daughter of Cronos); Titan; Hyperion (a Titan); Iapetus (a Titan); Phoebe (another name for Artemis, goddess of the moon).
The newest satellites were named for Gallic (Gaul, or ancient France), Norse, and Inuit (Eskimo) giants: Kiviuq, Ijiraq, Paaliaq, Skadi, Albiorix, Erriapo, Siarnaq, Tarvos, Mundilfari, Suttung, Thrym, and Ymir.
Saturn has 56 known moons, nine of which were announced in June 2006 and are known by the temporary designations S/2004 S19 and S/2006 S1 through S8.
URANUS
Uranus was named for the Greek god of the sky. The astronmer William Lassell, who discovered two of Uranus' satellites in 1851, started the tradition of naming all of the planet's satellites for characters in the work of William Shakepseare and Alexander Pope.
SATELLITES: Cordelia (daughter of Lear in Shakespeare's “King Lear”); Ophelia (daughter of Polonius, fiance of Hamlet in Shakespeare's “Hamlet”); Bianca (daughter of Baptista, sister of Kate in Shakespeare's “Taming of the Shrew”); Cressida (title character in Shakespeare's “Troilus and Cressida”); Desdemona (wife of Othello in Shakespeare's “Othello”); Juliet (heroine of Shakespeare's “Romeo and Juliet”); Portia (rich heiress in Shakespeare's “Merchant of Venice”); Rosalind (daughter of the banished duke in Shakespeare's “As You Like It”); Belinda (character in Pope's “Rape of the Lock”); Puck (mischievous spirit in Shakespeare's “A Midsummer Night's Dream”); Miranda (the heroine of Shakespeare's “The Tempest”); Ariel (a benevolent spirit in Shakespeare's “The Tempest”); Umbriel (a malevolent spirit in Pope's“ Rape of the Lock”); Titania (the queen of the fairies in Shakespeare's “A Midsummer Night's Dream”); Oberon (the king of the fairies in “A Midsummer Night's Dream”); Caliban (the brutish slave in Shakespeare's “The Tempest”); Sycorax (Caliban's mother in “The Tempest”); Prospero (the rightful Duke of Milan in “The Tempest”); Setebos (a false god worshiped by Caliban in “The Tempest”); Stephano (a drunken butler in “The Tempest”); Trinculo (a jester in “The Tempest”).
There are 27 known moons of Uranus. Ten of the moons, being closer to the planet, have faster periods of revolution (8–15 hours) than their more distant relatives.
NEPTUNE
Neptune, a blue planet, was named for the Roman god of the sea.
SATELLITES: Naiad (a group of Greek water nymphs who were guardians of lakes, fountains, springs and rivers); Thalassa (Greek sea goddess); Despina (daughter of Neptune); Galatea (one of the attendants of Neptune); Larissa (a lover of Neptune); Proteus (a Greek sea god); Triton (the sea-god son of Poseidon/Neptune); Nereid (the Nereids, a group of fifty daughters, were attendants of Neptune).
In Jan. 2003, astronomers from the Harvard-Smithsonian Center for Astrophysics and the National Research Council of Canada announced that three new moons had been discovered orbiting Neptune. Two more moons were announced later in 2003, bringing the total to 13. Five other recently discovered satellites are still unnamed.
PLUTO
Pluto, the outermost planet in our solar system, was named after Roman god of the underworld, who was able to render himself invisible. In Aug. 2006, the International Astronomical Union (IAU) declared Pluto to be a dwarf planet.
SATELLITE: Charon (the mythological boatman who ferried souls across the river Styx to Pluto for judgement).
Two new moons were sighted by the Hubble Space Telescope in Oct. 2005 and confirmed in Feb. 2006, bringing Pluto's satellites to three.***
NEW DWARF PLANET NAMED ERIS
Discovery
In July 2005, a team from the California Institute of Technology headed by astronomer Michael Brown announced the discovery of a possible "tenth planet," which was temporarily called 2003 UB-313. This most distant object so far found in our solar system is larger than Pluto and takes 560 years to orbit the Sun. Most planets circle the Sun very near the same plane as Earth's orbit, but the new object's orbit is off this elliptic plane by about 44 degrees. Astronomers studying this object nicknamed it "Xena" and in 2006 discovered it had a moon, nicknamed "Gabrielle."
Xena's size helped spark the drive for a decisive definition of a planet. Under a proposal presented at the start of the triennial assembly of the International Astronomical Union (IAU) in 2006, the union would have added two more planets to the solar system: Xena and the asteroid Ceres.
Dwarf planet
After much debate, the union decided to classify Xena, Pluto, and Ceres as dwarf planets. Other recently found Trans-Neptunian Objects (TNOs) expected to be declared dwarf planets in this class are Varuna (2000), Ixion (2001), Quaoar (2002), Orcus (2003), and Sedna (2004).
The IAU General Assembly in Prague on August 24, 2006, reduced the solar system from nine to eight planets on the vote of less than 5% of nearly 9,000 members. The new president, Catherine Cesarsky—the first woman to head the union—will have to deal with refining the decisions made at the assembly. A number of astronomers are unhappy with the outcome of the vote and it is expected that the 2009 general assembly in Rio de Janeiro will have more to say on the subject.
New name
On September 13, 2006, the IAU announced the official name of the object formerly known as Xena. The new name, which had been submitted by Michael Brown, is Eris, the Greek goddess of strife or discord. Eris's moon is now Dysnomia, daughter of Eris.
The goddess Eris at a wedding party tossed a golden apple into the crowd of guests inscribed kallisti, or "for the prettiest." This led to an argument among the goddesses Athena, Hera, and Aphrodite over which deserved the apple. This seems appropriate for the name of a object which sparked intense debate among astronomers and the general public about the definition of a planet, leading to Pluto getting kicked out of the club amidst vocal protests.***
PLUTO DEMOTED!
(Not a planet anymore)
New Definition of a Planet
The International Astronomical Union (IAU) voted on an official definition of the word "planet" at their general assembly in Prague on Aug. 24, 2006. Celestial bodies must meet the following conditions in order to be classified as planets: (1) The object must be in orbit around a star, while not being itself a star, (2) the body must be massive enough for its own gravity to pull it into a nearly spherical shape, and (3) the object has cleared the neighborhood around its orbit. The last criterion is the one that led to Pluto's demotion. While the exact parameters of "clearing the neighborhood" have not been set, the other planets have either assimilated or repulsed most other objects in their orbits, and each has more mass than the combined total of everything else in its area. The same cannot be said for Pluto, which has turned out to be one of many objects in its orbit.
Pluto is Out!
Pluto's new classification is "dwarf planet," while the eight planets remaining—Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune—are planets. The asteroid Ceres (classified a planet when first discovered in the 1801) and Eris (previously nicknamed "Xena") have joined Pluto as dwarfs. The IAU also has a dozen candidate planets awaiting future designation as dwarf planets: Sedna (2004), Orcus (2003), Quaoar (2002), Ixion (2001), Varuna (2000)—all found beyond Pluto; the asteroids Vesta, Pallas, Hygiea; and four yet unnamed bodies (2003 EL-61; 2005 FY-9; 2002 TX-300; 2002 AW-197).
Also defined was "Small Solar System Bodies" as all other objects except satellites orbiting the Sun. These include the asteroids, Trans-Neptunian Objects, comets and other small bodies.***
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