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by: Zarif Saabab Planets In our Solar System Diameter: 4,880 km Distance to Sun: 57,910,000 km (0.38 AU) Orbital Period: 88 Days Surface Area: 75,000,000 km2 Number of Moons: 0 Axial Tilt: 0.01º Mercury is currently the smallest planet in the so- lar system. It is the also the closest planet to the sun. The time it takes for one whole axial rotation is 58 Earth days so within two-axial rotation a whole Mercurial year would pass. Mercury can be mainly seen in the sky during dawn or dusk. The name of the plan- et comes from a Roman winged messenger of the gods because of its fast or- bital speed around the sun when compared to other planets. Mercury has a very thin atmosphere compris- ing of only trace elements of potassium, argon, and oxygen. This is because Mercury is closest planet to the Sun and it is being constantly being bombard- ed by incredible amounts of solar heat and radiation. Mercury has a very wide range of temperatures from –183ºC to 425ºC al- though it has an average temperature of 170ºC. Its surface mainly contains rocks with high Iron con- tent. Mercury has hundred of large craters all over the surface of the planet by meteorites easily breaking through the imsy atmos- phere. Most of the planet has not been mapped with much detail, so its distin- guishable characteristics are not very well known. The rst known observa- tion of Mercury was over 5,000 years ago by an an- cient civilization called the Sumerians. Mercury has an incredibly small axial tilt being basically at right angles to the Sun, so that the Sun is always over the equator at any time of its year. 1 Mercury Diameter: 12,100 km Distance to Sun: 108,200,000 km (0.72 AU) Orbital Period: 225 Days Surface Area: 460,000,000 km2 Number of Moons: 0 Axial Tilt: 177.3º Venus is the second plan- et from the Sun and is the closest planet to Earth, with the closest distance being 38,200,000 km. The time it takes to make one whole axial rotation is 243 Earth days, so that it takes longer for Venus to make an axial rotation than it does to make a whole orbit of the Sun. Venus is sometimes bright enough to be seen in the day but during a clear night Venus shines brighter than any other star in the night sky. The name of Venus also comes from Roman mythology, specically the Roman goddess of love. Its atmosphere comprises of thick and dense carbon dioxide as well as nitrogen and sulfuric acids. Venus is only one of two planets in the solar system that has a retrograde spin which means that it spins in the opposite directions on its axis when compared to the other planets. The highest temperature in Venus is 500ºC near the equator of the planet, but can get as low as 45ºC at the cloud tops of the plan- et, but its average surface temperate is 470ºC making it the hottest planet in the solar system. Its surface is manly rocky and hard with numerous volcanoes all over the planet. Venus is the hottest planet in the solar system because its thick atmosphere and green house gases traps huge amounts of heat from the Sun. The Babylonians were the rst to record observations of the planet over 3,600 years ago. 2 Venus Diameter: 12,756 km Distance to Sun: 149,600,000 km (1 AU) Orbital Period: 365 Days Surface Area: 510,000,000 km2 Number of Moons: 1 Axial Tilt: 23.4º Earth, the third planet from the Sun and the only planet in this solar system that can support life. Earth is also the largest of the terrestrial or inner planets, which comprises of Mercu- ry, Venus, Earth and Mars. The continents on Earth have been formed by mil- lions of years of plate tec- tonic movements on the Earths crust. The unit AU or Astronomi- cal Unit comes from the average distance between the Earth and the Sun; it has become a standard unit when measuring the distance from a planet to the Sun. The time it takes for one planetary rotation on its axis is about 23.93 Earth hours. Alternate names for Earth are Terra or Gaia, but the name Earth comes from Old English name Eorthe. The atmos- phere mainly comprises of nitrogen and oxygen along with other traces of carbon dioxide, some water vapor and other gases. The atmosphere also pro- tects the surface of the planet by shielding harmful UV rays from the Sun. More than three quarters of the Earths surface is covered with water, which include rivers, lakes, seas, oceans, glaciers, and ice caps. The lowest temperature ever recorded on Earth is –89ºC and the highest is 58ºC, with an average tempera- ture of 22ºC. The surface ranges from tall moun- tains to deep valleys, but mainly covered with wa- ter. Over 3,000 years ago early Greek philosophers thought that Earth was a at dish. Earth has only one moon called Luna, and its pull of gravity is what causes the rise and fall of the oceans called tides. 3 Earth Diameter: 6,780 km Distance to Sun: 227,940,000 km (1.52 AU) Orbital Period: 687 Earth Days Surface Area: 144,000,000 km2 Number of Moons: 2 Axial Tilt: 25.2º The forth planet from the Sun, Mars is the last plan- et before the main aster- oid belt separating the in- ner terrestrial planets from the Gas Giants. The sur- face of Mars has been very well documented and huge maps of the planet have been made. The axial rota- tion of the planet is 24.62 Earth hours, being very similar to that of Earth, but one orbit around the Sun would take almost twice as long when compared to Earth. The name Mars also comes from the Roman god of war, but it is also some- times called the Red Plan- et because of the reddish orange hue of the planet. The planet is bright enough to be seen with the naked eye on a clear night sky. The atmosphere is mainly comprised of carbon diox- ide with small amounts of nitrogen and argon, with small traces of oxygen and carbon monoxide and wa- ter vapor. The surface is comprised of mainly Iron Oxide in the form of dust and rock as well as many big vol- canoes, deep valleys, and large plains. Water in the form of ice can be found on the north polar ice cap of Mars, features resembling riverbeds, estuaries and shorelines have led scien- tist to speculate whether life ever existed on Mars. Many space probes, landers and rovers were sent to Mars but none of them reported any signs of life on the planet. Over 4,000 years ago ancient Egyptian astronomers were the rst to observe Mars. 4 Mars Diameter: 142,984 km Distance to Sun: 778,330,000 km (5.20 AU) Orbital Period: 4,333 Earth Days (11.8 Earth Years) Surface Area: 61,400,000,000 km2 Number of Moons: 60+ Axial Tilt: 3.13º The fth planet from the Sun and the rst of the outer planets, Jupiter is the largest planet in the so- lar system. The four outer planets such as Jupiter are known as Gas Giants be- cause they are not mainly comprised of solid matter. Jupiter has one of the fast- est axial rotation period as it just takes the planet only 9.92 hours to make one ro- tation on its axis. Jupiter is the third brightest ob- ject in the night sky after the Moon and Venus. The name of Jupiter yet again comes from Roman mythol- ogy, this time from the Ro- man king of the gods, and is also sometimes called Jove. The atmosphere is mostly of hydrogen, hydro- gen sulde and some he- lium along traces of meth- ane, water vapor, ammonia and other gases. Due to its huge gravitational pull Ju- piter has over 60 known natural satellites that orbit around it. Jupiter like the other gas giants is a very cold planet with the lowest tempera- ture being –170ºC and the highest temperature being –110ºC, but has an average temperature of –163ºC. Jupiter has a small molten core although there is no clear surface that can be seen as it is surround- ed by many different lay- ers of metallic, liquid, and gaseous hydrogen as well as other gases. Jupiter is in fact so heavy that it is twice as heavy than all the other planets put togeth- er, but is still only 1/1000 the mass of the Sun. Jupi- ter was rst known to the Greeks then the Romans over 3,000 years ago. Jupiter 5 Diameter: 120,536 km Distance to Sun: 1,420,400,000 km (9.54 AU) Orbital Period: 10,759 Earth Days (29.5 Earth Years) Surface Area: 42,700,000,000 km2 Number of Moons: 50+ Axial Tilt: 26.7º Saturn the sixth planet from the Sun is the sec- ond largest planet in the solar system. The density of the planet is the lowest in the solar system; in fact it is so low that it is lower than the density of water. One whole axial rotation is approximately 10.77 Earth hours making it the second fastest behind Jupiter. Sat- urn can usually be seen in the night sky but it is not nearly as bright as the oth- er planets closer to Earth. The name comes from the Roman god of farming, civilization, and prosperity. Its atmosphere much like that of Jupiter comprises of mainly hydrogen and small amounts of helium as well as trace elements of meth- ane, water vapor, and am- monia. The most distinc- tive quality of Saturn is its rings that surround the planet in its equator, these rings are made of billions of ice and rock particles that reect sunlight to sparkle. The surface temperatures, much like Jupiter are very cold with the lowest tem- perature being –190ºC and the highest being –120ºC, with an average tempera- ture of –130ºC. It does have a solid molten core at a depth of 52,300 km below the surface that is surrounded by layers of metallic and molecular hy- drogen much like Jupiter. Due to its light density and fast speed the planet has a bulge in the equator, so it is wider than it is tall. Over 2,500 years ago the Greeks and then the Romans had rst known and document- ed the planet Saturn. 6 Saturn Diameter: 51,118 km Distance to Sun: 2,870,990,000 km (19.22 AU) Orbital Period: 30,799 Earth Days (84.1 Earth Years) Surface Area: 8,080,000,000 km2 Number of Moons: 30+ Axial Tilt: 97.8º The seventh planet from the Sun, Uranus is the third gas giant and also the sec- ond last planet it the solar system. It is more speci- cally known as an ice gi- ant and is sometimes pro- nounced as yur-in-as. Its axial rotation is 17.2 Earth hours. Uranus is the one of two planets that cannot be seen by the naked eye, and have been discovered by the use of telescopes. The name for Uranus does not come from the Romans but in fact comes from the Greek god of the heavens, had the name come from the Romans it would have been called ‘Caelus’. Its at- mosphere is quite similar to that of Jupiter and Sat- urn as it mainly contains hydrogen as well as some helium and methane with traces of ammonia. The tilt of axis is almost at right angles to the Sun so that it seems like the entire plan- et is on its side. Its surface temperature is colder than both Jupiter and Saturn with the lowest temperature being –214ºC and the highest tempera- ture being –200ºC, it has an average temperature of –205ºC. Its surface is very gassy with solid sur- faces deep below the at- mosphere, which contains mainly rock and ice. The mass of Uranus is more than 27 times that of the mass of Earth. Uranus and Neptune were the only two planets that were not know to ancient civilization due to its great distance. The rst record of Uranus was a dim star-like object in 1660 but it was in 1781 when it was rst identied as a planet. 7 Uranus