The Planets   Click to go to information table          The Sun Diameter (km): 1 392 000 Mass (Earth=1): 332 946 Surface gravity (Earth=1): 27.9 Average surface temperature (oc): 5 500 Length of rotation: Equatorial=25 Earth days, Polar=35 Earth days Number of rings: 0 Approximate age: 4.6 Approximate core temperature: 15 000 000oc Star type: Yellow main sequence star Atmosphere composition: Hydrogen and helium      The Sun is the star at the centre of the solar system. It is about 4.6 billion years old and will continue to shine as it does now for about 5 billion years. The sun provides our solar system with heat and light; without it we would not even exist. It also emits harmful radiation like gamma rays and ultraviolet light which we are protected from; by Earth’s atmosphere.          Planet: Mercury Diameter (km): 4 878 Mass (Earth=1): 0.55 Surface gravity (Earth=1): 0.38 Average surface temperature (oc): -170 to 430 Length of day (in Earth hours/day/years): 58.65 days Length of year (in Earth hours/day/years): 88 earth days Distance from Sun (million km): 45.9 to 69.7 Number of rings: 0 Number of known moons: 0 Volume (Earth=1): 0.056 Speed of movement (around the sun): 172 332kmph / 47.89kmps Atmosphere composition: Principally of helium and hydrogen with little amounts of sodium, oxygen, neon, argon and potassium   Mercury is the closest planet to the sun and is the second smallest in our solar system. Its temperature ranges from 430oc from the sunlit areas to -170oc on the dark side. This dramatic temperature difference is due to the fact that Mercury’s atmosphere is virtually non-existent; consisting of only minute amounts of helium, hydrogen and various other gases captured from the solar wind.          Planet: Venus Diameter (km): 12 103 Mass (Earth=1): 0.81 Surface gravity (Earth=1): 0.86 Average surface temperature (oc): 464 Length of day (in Earth hours/day/years): 243.01 Earth days (retrograde orbit) Length of year (in Earth hours/day/years): 224.7 days Distance from Sun (million km): 107.4 to 109 Number of rings: 0 Number of known moons: 0 Volume (Earth=1): 0.86 Speed of movement (around the sun): 126 072kmph / 35.03kmps Atmosphere composition: about 92% Carbon dioxide, 3.5% nitrogen.    Venus is the second planet from the Sun yet also the hottest due to the high amount of carbon dioxide in its atmosphere; this causes the greenhouse effect. The high temperature, enormous atmospheric pressure 90 times that of Earth and its sulphuric acid clouds makes the environment extremely hostile. Nethertheless, space probes have radar mapped the surface and some probes have even landed on the surface and photographed the terrain, though only having lasted at most; a few hours.          Planet: Earth Diameter (km): 12 756 Mass (Earth=1): 1 Surface gravity (Earth=1): 1 Average surface temperature (oc): 15 Length of day (in Earth hours/day/years): 23.93 hours Length of year (in Earth hours/day/years): 365.26 days Distance from Sun (million km): 147.1 to 152.1 Number of rings: 0 Number of known moons: 1 (the moon) Volume (Earth=1): 0.86 Speed of movement (around the sun): 107 244kmph / 29.79kmps Atmosphere composition: 78% Nitrogen, 21% Oxygen and 1% water vapour, argon, carbon dioxide and other trace gases    The Earth is the third planet from the Sun and also the one where we live. It is the largest and densest rocky planet and the only one known to support life. The Earth’s atmosphere protects it from the sun’s harmful radiation and meteorites but still trapping enough heat to support life. About 70% of Earth is covered by water; which at present is not found on the surface of any other planet in liquid form. The Earth has one moon which is large enough for both bodies to be considered as a double planet system.          Planet: Mars         Diameter (km): 6 786 Mass (Earth=1): 0.11 Surface gravity (Earth=1): 0.38 Average surface temperature (oc): -63 Length of day (in Earth hours/day/years): 24.62 hours Length of year (in Earth hours/day/years): 1.88 years Distance from Sun (million km): 206.7 to 249.1 Number of rings: 0 Number of known moons: 2 (Phobos, Deimos) Volume (Earth=1): 0.15 Speed of movement (around the sun): 86 868kmph / 24.13kmps Atmosphere composition: 95% Carbon dioxide, 2.7% Nitrogen, 1.6% Argon, 0.7% Oxygen, carbon monoxide and water vapour.   The red planet; Mars is the fourth planet from the sun and the outermost rocky planet. When astronomers first observed the surface of Mars they observed what were thought to be signs of life on Mars; canals and vegetation. Though now these ‘canals are optical illusions and the dark patches ‘vegetation?are where the red dust on the surface ahs been blown away. The solar system’s largest volcano exists on Mars; the 600km wide and 25km high Olympus Mons. The Martian atmosphere is much thinner than Earth’s with only a few clouds and morning mists.          Planet: Jupiter Diameter (km): 142 984 Mass (Earth=1): 318 Surface gravity (Earth=1): 2.5 Average surface temperature (oc): -120 Length of day (in Earth hours/day/years): 9.92 hours Length of year (in Earth hours/day/years): 11.86 years Distance from Sun (million km): 740.3 to 815.7 Number of rings: 1 Number of known moons: 16 (Metis, Adrastea, Amalthea, Thebe, Io, Europa, Ganymede, Callisto, Leda, Himalia, Lysithea, Elara, Ananke, Carme, Pasiphae, Sinope) Volume (Earth=1): 1 323 Speed of movement (around the sun): 47 016 kmph / 13.06 kmps Atmosphere composition: 90% Hydrogen, 10% Helium with traces of ammonia, methane and water vapour.    Jupiter is the fifth planet from the sun, the first of four  gas giants and is also the biggest planet in the solar system. It has a diameter 11 times bigger than Earth and a mass 2.5 times bigger than the combined mass of the eight other planets. The rapid rotation of Jupiter (one rotation takes 9 hours 55 minutes) causes its clouds to form belts and zones that encircle the planet parallel to the equator. With these belts and zones, turbulence causes the formations of red spots and white ovals; huge storm systems. The prominent Great Red Spot consists of spiralling column of clouds that is three times wider than Earth and eight kilometres above the outer cloud layer. One of Jupiter’s moons called Europa is 3 138km in diameter, covered in ice. Scientists say that under the ice layer there may be water, which may then support life.          Planet: Saturn Diameter (km): 120 536 Mass (Earth=1): 95,18 Surface gravity (Earth=1): 1.1 Average surface temperature (oc): -180 Length of day (in Earth hours/day/years): 10.67 hours Length of year (in Earth hours/day/years): 29.46 years Distance from Sun (million km): 1 347 to 1 507 Number of rings: 7 Number of known moons: 18 (Pan, Atlas, Prometheus, Pandora, Epimethius, Janus, Mimas, Enceladus, Tethys, Telesto, Calypso, Dione, Helene, Rhea, Titan, Hyperion, Iapetus, Phoebe) Volume (Earth=1): 744 Speed of movement (around the sun): 34 812 kmph / 9.64 kmps Atmosphere composition: 94% Hydrogen, 6% helium with traces of ammonia, methane and water vapour.    Saturn is the sixth planet from the sun, the second largest, and has rings extending out 420 000km form the planet’s surface. Saturn’s clouds form belts and zones like Jupiter but are obscured by the overlying haze. One rotation takes 10 hours and 40 minutes. The core is thought to be composed of rock and ice, surrounded by an inner mantle of liquid metallic hydrogen (liquid hydrogen which acts like a metal). There are 19 moons orbiting this planet, some of which share orbits; astronomers believe that these moons may have originated from a single satellite that broke up.          Planet: Uranus Diameter (km): 51 118 Mass (Earth=1): 14.5 Surface gravity (Earth=1): 1.1 Average surface temperature (oc): -210 Length of day (in Earth hours/day/years): 17.23 hours (retrograde orbit) Length of year (in Earth hours/day/years): 84.01 years Distance from Sun (million km): 2 735 to 3 004 Number of rings: 11 Number of known moons: 15 (Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck, Miranda, Ariel, Umbriel, Titania, Oberon) Volume (Earth=1): 67 Speed of movement (around the sun): 24 516 kmph / 6.81 kmps Atmosphere composition: 85% Hydrogen, 12% helium and 3% methane.    Uranus is the seventh planet from the sun and also the third largest. The atmosphere contains traces of methane which gives the planet a blue-green hue, though the planet is quite featureless with only a few methane clouds being spotted so far in the atmosphere. Uranus is quite unique in that it rolls on its side along the orbital path around the sun.          Planet: Neptune Diameter (km): 49 528 Mass (Earth=1): 17.14 Surface gravity (Earth=1): 1.1 Average surface temperature (oc): -220 Length of day (in Earth hours/day/years): 16.12 hours Length of year (in Earth hours/day/years): 164.79 years Distance from Sun (million km): 4 456 to 4537 Number of rings: 4 Number of known moons: 8 (Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Triton, Nereid) Volume (Earth=1): 57 Speed of movement (around the sun): 19 548 kmps / 5.43 kmps Atmosphere composition: 85% Hydrogen, 13% Helium and 2% methane.    Neptune is a gas planet with four rings and eight moons. Like Jupiter it also contains large cloud storms called the Great Dark spot (as wide as the Earth) and the Small Dark spot which are pushed around the planet by winds of about 2000 kilometres per hour. One of Neptune’s moons; Triton, has a temperature of -235oc making it the coldest object in the solar system.          Planet: Pluto Diameter (km): 2 300 Mass (Earth=1): 0.0022 Surface gravity (Earth=1): - Average surface temperature (oc): -220 Length of day (in Earth hours/day/years): 6.38days (retrograde orbit) Length of year (in Earth hours/day/years): 248.54 years Distance from Sun (million km): 4 425 to 7 375 (elliptical orbit sometimes closer than Neptune, other times farther away) Number of rings: 0 Number of known moons: 1 (charon) Volume (Earth=1): Unknown Speed of movement (around the sun): 17 063kmph / 4.74 kmps Atmosphere composition: Probably Methane mixed with nitrogen.   Pluto is the smallest planet in the solar system and is the farthest away. However, due to its elliptical orbit, it spends 20 years of its 248 year revolution around the sun inside the orbit of Neptune. Because Pluto is so small and so far away, little is known about it. It is a rocky planet, probably covered with ice and frozen methane. Its moon, Charon is large for a moon as it is half the size of its parent planet. Because of this size difference, sometimes Pluto and Charon are considered to be double planet systems.