Sun & the Planets

Sun

• Our brightest star has a diameter of 1.39x10⁶km and a mass of 1.989x10³⁰kg.
• Its surface temperature reaches 5800K but at the core it is 15.6x10⁶K.
• As with all gas stars, the outer layers rotate differently from the equator to the poles. At the equator, the rotation takes 25.4 days and near the poles it takes 36 days.
• Energy output of the sun is 386 billion billion MW. This is produced by nuclear fusion reactions (the combination of two atoms to produce one larger one with one nucleus). Each second about 700,000,000 tons of hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons of energy in the form of gamma rays.
• The sun also produces a solar wind, which is a low density stream of charged particles (electrons and protons) which can travel at speeds of approximately 450km/s

Mercury

• Closest planet to the sun and the second smallest
• Mercury is the name of the Roman god of commerce, travel and thievery
• Its orbit is highly eccentric, its distance from the sun ranges from 46 million km (at perihelion) to 70 million km (at aphelion).
• Rotates on its axis three times in two years of its orbit around the sun
• It has a very thin atmosphere which is constantly destroyed and replenished by the sun's solar wind; hence its temperture is not stable ranging from only 90K to 700K.
• Has a small magnetic field (1% of the earths) and no satellites.

Venus

• Second planet from the sun and the six largest
• Venus is the name of the Roman goddess of love and beauty
• A day in Venus (243 earth days) is longer than its year (224 earth days)
• It rotates in the opposite direction to the rotation of the earth and the period of Venus' rotation and of its orbit is synchronized so that it always presents the same face to the Earth when the two planets are at their closest approach.
• The astmosphere is composed of mainly carbon dioxide and has dense clouds composed of sulfuric acid. This combination has produced a green-house like effect on Venus and its temperature is higher than Mercury's even though it is about twice as far from the sun.
• Venus currently has active volcanoes like Earth with rocky eruptive material, driven by internal heat. Much of its surface is covered by lava flows.
• Has no magnetic field and no satellites.

Earth

• Third planet from the sun, fifth largest and the densest planet
• Wasn't until the 16th century did people understand that the earth is just another planet .. thanks largely to Copernicus.
• The Earth is divided into seven layers (depth in km):

• The earths total composition is :
  • 34.6% Iron
  • 29.5% Oxygen
  • 15.2% Silicon
  • 12.7% Magnesium
  • 2.4% Nickel
  • 1.9% Sulfur
  • 0.05% Titanium
• The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water.
  • The tiny amount of carbon dioxide in the atmosphere at any time is extremely important for the maintenance of the Earth's surface temperature. The greenhouse effect raises the average surface temperature about 35�C above what it would otherwise be (from a frigid -21�C to a comfortable +14�C)
• 71% of surface is covered in water
• The Earth has only one satellite, the moon, the interaction between the two slows the Earth's rotation by about 2 milliseconds per century.

Mars

• Fourth planet from the Sun and the third smallest
• Mars was the Roman God of War
• Orbit is highly elliptical, causing the surface temperature to range between 140K to 300K (-133�C to 27�C)
• Olympus Mons, the highest mountain in the solar system, exists on Mars - 24km high, 500km wide at the base
• Mars has a very thin atmosphere composed mostly of carbon dioxide (95.3%) plus nitrogen (2.7%), argon (1.6%) and traces of oxygen (0.15%) and water (0.03%).
  • Its thin atmosphere produces a weak greenhouse effect, raising the surface temperature by only 5�C
• Mars has two satellites which orbit very close to the surface (Named after brothers, sons of Ares (equivalent to Mars) and Aphrodite (equivalent to Venus):

Jupiter

• Fifth planet from the sun and is twice as big as all the other planets combined.
• Jupiter (a.k.a. Jove) was the Roman King of the Gods, the ruler of Olympus and the patron of the Roman state. His Greek equivalent was Zeus.
• The first of the gaseous planets, it is thought to have a rocky core surrounded by gaseous material which gets denser with depth. The diameter quoted is for the level where the gas pressure is 1 atmosphere (= 1.013 bars = 1.03 kg/cm² = 14.7 pounds/inch², standard atmospheric pressure at sea level on Earth.
• Consists of three layers:
  • The internal core composed of rocky material probably about 12.5 times larger than Earth
  • Surrounding the core is the layer of Liquid Metallic Hydrogen, the main bulk of the planet - Hydrogen in this form is only possible under pressures of greater than 4 million atmospheres.
  • The outermost layer is composed primarily of hydrogen and helium which is liquid in the interior and gaseous further out. Water, carbon dioxide, and methane are also present in small amounts
• As with all gaseous planets, there are high velocity winds which are confined to wide bands of latitude which give the planets there appearance. The array of colours are largely due to chemical reactions occuring between the trace elements of the atmosphere and also indicate the depth of these reactions; blue for deepest and red for shallowest.
• The Great Red Spot is a high-pressure region whose cloud tops are significantly higher and colder than the surrounding regions.
• Jupiter has rings like Saturn's, but much fainter, darker, smaller and contain no ice. They are probably composed of dust and rocky material only.
• Jupiter has 16 known moons. There are also 11 moons which have been recently discovered but have not yet been officially confirmed or named. The four largest moons (Galilean - Io, Europa, Ganymede, Callisto) are gradually slowing down Jupiters rotation due to the tidal drag they produce. Also, these forces are changing the orbits of the moons, very slowly forcing them away from Jupiter. Jupiter has 8 irregular satellites, which means they either have highly non-circular orbits or orbit at a significant inclination to Jupiters equator.

Saturn

• Sixth planet from the Sun and the second largest.
• Saturn was the Roman God of Agriculture (his Greek equivalent was Cronus, Zeus' father.
• Least dense of all the planets; contains 75% hydrogen, 25% helium with traces of water, methane, ammonia and rock particles.
• Internally, Saturn is like Jupiter with a rocky core, liquid metallic hydrogen layer and an outer layer of trace elements. Saturn has traces of ice as well.
• When visualised, Saturn has a lot of Jupiters features, banding effects because of high velocity winds and spots of irregularity in the atmosphere (like the Great Red Spot).
• Saturn has three very bright rings and four additional faint ones. The ring particles seem to be composed primarily of water ice, and may also include rock particles with coats of ice.
  

• Some of Saturns moon's play an important role in keeping the rings "in-line". Also known as "shepherd satellites/moons" they limit the size and movement of a planetary ring through gravitational forces.
• Saturn has 18 moons. There are another 12 which have been confirmed recently but not yet named.
• Tethys and Dione share their orbits with other moons in a fixed position. Joseph L. Lagrange(1736-1813) showed that three bodies can lie at the apexes of an equilateral triangle which rotates in its plane. If one of the bodies is sufficiently massive compared to the other, then the configuration may be stable. In the case of Tethys, Tethys lies at point S, Telesto leads at point L4 and Calypso trails at L5.

Name	Distance (000 km)	Diameter (km)	Discoverer, Date	Distinguishing Feature
Pan	134	20	Schowalter, 1990	Pan was the god of woods, fields, and flocks; half human and half goat. Wave patterns in the edge of Saturn's rings predicted Pan's size and location, leading to its discovery.
Atlas	138	28	Terrile, 1980	Atlas was a Titan condemned by Zeus to support the heavens upon his shoulders! "Shepherd satellites" of A ring.
Prometheus	139	92	Collins, 1980	Prometheus was a Titan who stole fire from Olympus and gave it to humans. Inner shepherd satellites of F-ring.
Pandora	142	92	Collins, 1980	Pandora was the first woman, bestowed upon humankind by Zeus, as a punishment for Prometheus' theft of fire. Entrusted with a box, she opened it and released all the evils of human life. Outer shepherd satellite of F-ring
Epimetheus	151	114	Walker, 1980	Atlas's brother and Pandora's husband. It and Janus are co-orbital, their orbital radii differ by only 50 km. Their orbital velocities are nearly equal. As they approach each other they exchange a bit of momentum to boost the lower one into a higher orbit and to drop the higher one to a lower orbit. They exchange places about once in 4 years.
Janus	151	178	Dollfus, 1966	Janus was the god of gates and doorways, depicted with two faces looking in opposite directions. Orbital partner of Epimetheus, but appears to be its elder.
Mimas	186	392	Herschell, 1789	Mimas was one of the Titans slain by Hercules. The surface is dominated by an impact crater 130 km across, called Herschel, almost 1/3 of the moon's diameter.
Enceladus	238	498	Herschell, 1789	Enceladus was a Titan who was defeated in battle and buried under Mount Etna by Athena. It has the highest albedo {ratio of incident light to reflected light (>0.9)} of any body in the solar system.
Tethys	295	1060	Cassini, 1684	Tethys was a Titaness and sea goddess, sister and wife of Oceanus. Surface dominated by a huge impact crater 400 km across, called Odysseus, nearly 2/5 of the moon's diameter.
Telesto	295	30	Reitsema, 1980	Telesto was a daughter of Oceanus and Tethys. Orbital partner of Tethys, leads by 60�.
Calypso	295	26	Pascu, 1980	Calypso was a sea nymph who delayed Odysseus on her island for seven years. Orbital partner of Tethys, trails by 60�.
Dione	377	1120	Cassini, 1684	Dione was the mother of Aphrodite, by Zeus. Composed primarily of water ice and denser material like silicate rock. Shares its orbit with Helene.
Helene	377	32	Lasques, 1980	Helene is the name of an Amazon who battled with Achilles. Orbital partner of Dione, leads by 60�.
Rhea	527	1530	Cassini, 1672	Rhea was the sister and wife of Cronus. Second largest of Saturn's moons. Composed primarily of water ice with rock making up <1/3 of its mass.
Titan	1222	5150	Huygens, 1655	Titans were a family of giants, who sought to rule the heavens but were overthrown Zeus' family. Largest of Saturns moons. Only moon in solar system that has a significant atmosphere (its pressure is 50% higher than Earths).
Hyperion	1481	286	Bond, 1848	Hyperion was a Titan. Most irregularly shaped moon in the solar system and has the lowest albedo of all Saturns moons.
Iapetus	3561	1460	Cassini, 1671	Iapetus was a Titan, son of Uranus, father of Prometheus and Atlas. Iapetus is inclined almost 15 degrees to Saturns equator. Its albedo is significantly different on its two hemispheres that Cassini noted he could see Iapetus only on one side of Saturn and not on the other.
Phoebe	12952	220	Pickering, 1898	Phoebe is the daughter of Uranus and Gaia. Albedo is very low (.05). Its orbit is inclined almost 175�. Phoebe is so different to Saturn's moons, that it may be a captured asteroid or Kuiper Belt object. Only irregular satellite of Saturn.

Uranus

• Seventh planet from the sun and third largest.
• Uranus is the ancient Greek deity of the Heavens, the earliest supreme god.
• Unlike all the other planets, Uranus spins on its axis which is almost parallel to its orbit (tilt of axis 97.86�). So its pole (north or south is still debated) is facing the sun.
• Composed of rock and ice, with only about 15% hydrogen and a little helium.
• Its atmosphere is about 83% hydrogen, 15% helium and 2% methane.
• Like the other gaseous planets, Uranus has bands of high velocity clouds but they are very faint.
• Uranus appears blue because the red light is absorbed by the methane in the atmosphere.
• Its magnetic field is odd in that it is not centered on the center of the planet and is tilted almost 60 degrees with respect to the axis of rotation.
• Uranus has 11 rings which are dark but composed of large particles as well as dust.The darkest is Epsilon, the outer most ring.
• Uranus has 20 named moons (including 5 irregular moons, recently discovered) plus 1 recently discovered but yet to be named.

Name	Distance (000 km)	Diameter (km)	Discoverer, Date	Distinguishing Feature
Cordelia	50	26	Voyager 2, 1986	Cordelia is a daughter of Lear in Shakespeare's King Lear. Appears to be the inner shepherd satellite for the Epsilon ring
Ophelia	54	32	Voyager 2, 1986	Ophelia is the daughter of Polonius in Shakespeare's Hamlet. Appears to be the outer shepherding satellite for Uranus's Epsilon ring.
Bianca	59	44	Voyager 2, 1986	Bianca is the sister of Katherine in Shakespeare's Taming of the Shrew. Very dark (albedo < 0.1).
Cressida	62	66	Voyager 2, 1986	Cressida is the daughter of Calchas in Shakespeare's Troilus and Cressida. Very dark (albedo < 0.1).
Desdemona	63	58	Voyager 2, 1986	Desdemona is the wife of Othello in Shakespeare's Othello. Very dark (albedo < 0.1).
Juliet	64	84	Voyager 2, 1986	Juliet is the tragic heroine in Shakespeare's Romeo and Juliet. Very dark (albedo < 0.1).
Portia	66	110	Voyager 2, 1986	Portia is a rich heiress in Shakespeare's Merchant of Venice. Very dark (albedo < 0.1).
Rosalind	70	54	Voyager 2, 1986	Rosalind is a daughter of the banished Duke in Shakespeare's As You Like It. Very dark (albedo < 0.1).
Belinda	75	68	Voyager 2, 1986	Belinda is the heroine in Alexander Pope's The Rape of the Lock. Very dark (albedo < 0.1).
1986U10	76	80	Karkoschka 1999	Yet to be named, its orbit is nearly identical to Belinda.
Puck	86	154	Voyager 2, 1986	Puck is a mischievous fairy in Shakespeare's Midsummer-Night's Dream. Very dark (albedo < 0.1).
Miranda	130	472	Kuiper, 1948	Miranda is a daughter of the magician Prospero in Shakespeare's The Tempest. Pictures taken by Voyager 2 showed that its surface is very irregular, young and old, with lots of canyons and terraced layers.
Ariel	191	1158	Lassell, 1851	Ariel is a mischievous airy spirit in Shakespeare's The Tempest. Its surface is a mixture of cratered terrain and interconnected valleys hundreds of kilometers long and more than 10 km deep.
Umbriel	266	1170	Lassell, 1851	Umbriel is a character in Alexander Pope's The Rape of the Lock. Has a heavily cratered surface and is very dark.
Titania	436	1578	Herschel, 1787	Titania is the Queen of the Fairies and wife of Oberon in Shakespeare's Midsummer-Night's Dream. Largest of Uranus' moons. Relatively young surface thats heavily cratered and has interconnected valleys, like Ariel.
Oberon	583	1522	Herschel, 1787	Oberon is the King of the Fairies and husband of Titania in Shakespeare's Midsummer-Night's Dream. Heavily cratered surface and has large faults.
Caliban	7169	80	Gladman, 1997	Caliban was the slave of magician Prospero in Shakespeare's play The Tempest. Irregular moon, red in colour, may be a captured asteroid from Kuiper Belt. The orbits are retrograde and highly inclined.
Stephano	7948	30	Gladman, 1999	Stephano was a butler on Ariel's ship who plotted with Caliban to murder Prospero in Shakespeare's play The Tempest.Irregular satellite of Uranus.
Sycorax	12213	160	Nicholson, 1997	Father of Caliban, he imprisoned Ariel for disobedience in Shakespeare's play The Tempest. Irregular moon, red in colour, may be a captured asteroid from Kuiper Belt. The orbits are retrograde and highly inclined.
Prospero	16568	40	Holman, 1999	Prospero was a powerful magician who enslaves Ariel in Shakespeare's play The Tempest. Irregular satellite of Uranus.
Setebos	17681	40	Kavelaars, 1999	Setebos was the god of Sycorax. Irregular satellite of Uranus.

Neptune

• In Roman mythology Neptune was God of the Sea. His Greek equivalent was Poseidon.
• Although its diameter is less than that of Uranus, it has a higher mass.
• When Uranus was discovered, its orbit did not fit Newtons laws and therefore another planet was perturbing its orbit leading to Neptunes discovery.
• Because of Pluto's highly eccentric orbit, Neptune is sometimes the furthest planet in our solar system for a few years.
• Neptune's composition is probably similar to Uranus' - various "ices" and rock with about 15% hydrogen and a bit of helium. Its atmosphere is mostly hydrogen and helium with a small amount of methane.
• It probably has internal heat source, radiating more than twice as much heat as it receives from the Sun.
• Like the other Gas Planets, Neptune has rapid winds confined to bands of latitude and large storms. Its winds are the fastest in the solar system, reaching 2000 km/hour. It also has "spots" like Jupiters "GRS" but much smaller.
• Neptune has rings which were at first thought to be arcs but Voyager 2 images showed them to be complete rings. They are actually four named (from outer to inner) - Adams, Unnamed, Leverrier and Galle.
• Has 8 known moons, 7 of which are small and the large Triton. Very little is known about any.

Pluto

• Furthest planet from the Sun and smaller than some of the solar systems moons.
• Pluto was the Roman God of the Underworld.
• Values for the mass and radius of Pluto are only estimates and may be out by almost 1%.
• Its orbit is highly eccentric, from Janury, 1979 to February, 1999 it was closer to the Sun than Neptune.
• Its orbittal inclination is much higher than the other planets and though it appears to cross the orbit of Neptune, the two planets won't collide.
  

• Pluto has only one moon, Charon. The combined mass of the planet and its moon is known more accurately than their individual values.
  • Charon is unusual in that it is the largest moon with respect to its primary planet in the Solar System (only about half the size of Pluto)
  • The pair are also unique because they both rotate synchronously to each other. So they are always have the same face to each other.

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