The Solar System

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 Our solar system comprises of eight planets , sun , and all the other asteroids , comets , meteoroids ,  dwarf planets etc. . The solar system was formed with the gravitational collapse of a giant molecular cloud . With its evolution going back to 4.6 billion years ago . Here’s a brief description of all the constituents of our solar system .

The Sun is a medium sized star . it has a diameter of 1,392,000 km (approximately 109 times the diameter of the earth) . The temperature of the sun’s surface is approximately 5000 degrees Celsius and its core’s temperature is 15 million degrees Celsius . The composition of the sun consists of 71% Hydrogen , 27% Helium and 2% of other heavier gases . Even though the sun is made up two lightest gases in the universe it weigh's 2000 trillion trillion tones which is about 3,00,000 times that of the earth. The sun was formed 4.6 billion years ago and in about 5 billion years it will enter its last phase thus becoming a red giant star. It provides energy to all the beings on earth and is the sole reason for life existing on Earth   

 Mercury was named after the messenger of the roman gods . It was named this as it is the fastest planet in the solar system with a speed of 1,07,000 mph, faster than any other planet in the solar system . One day on mercury is equal to 58.6 days on earth and one year on mercury lasts 88 earth days thus it orbits the sun in the fastest time compared to any other planets. Since Mercury has no atmosphere, temperatures here can plunge from -180 degrees Celsius at night to 430 degrees Celsius at day (hot enough to melt Lead). Mercury has no moons. Compared to earth Mercury has only 6% of its mass and therefore is so small that its gravity can hold on to very thin atmosphere. The crust and mantle of Mercury are made up of rock but its core is 75% of Iron. Caloris Basin is the largest crater on Mercury being 1300 km across and 2 km deep.  

 Venus was named after the roman goddess of beauty after it was seen very beautiful from the earth. It is the second planet from the sun and also the neighboring planet of the earth . The perihelion of Venus from the earth is at 107.4 km and aphelion at 109 km. Venus is the hottest planet in the solar system with a surface temperature being more than 470 degrees Celsius. The highest volcano of Venus is Maat Mons with a height of 6 km. The composition of atmosphere Venus mostly consists of Carbon Dioxide gas with the clouds which contain sulphuric acid, which is given by the planet’s volcanoes. The atmosphere of Venus is not transparent like the earths and thus it is very difficult for one to see what is happening inside the planet’s surface. The planet Venus is very identical with the earth in its size , having a diameter of 12,102km . Venus is also known as the evening star as it is visible from the earth in evening, although it can also be seen from the earth during sunrise.   

The Earth is third planet from the sun . It is the planet in which we live . It is the fifth largest planet in the solar system , and has diameter of 12,756 km with a circumference measuring 40,075 km at the Equator .  The planet is 149.6 km away from the sun at an average . The Earth is one of the four rocky planets along with Mercury , Venus and Mars and is the largest planet among them . Our planet is the most unique planet in the solar system as : ·

•  It has optimum temperature for life to exist · It has water · 
• It has an adequate composition of gases in its atmosphere for life to exist · 
• The Earth has the ozone layer present in its atmosphere which protects harmful ultraviolet radiation coming from the sun . 

The atmosphere of Earth mainly consists of Nitrogen (78%) , Oxygen ( 21%) and Carbon Dioxide (0.3%) and remaining mixture of other gases . The composition of Earth is mostly iron (35%) , oxygen (28%) , silicon (17%) , magnesium (15 %) and nickel (2.7%) . The earth was formed 4.5 billion years ago . It is believed that the moon was formed when rock the size of Mars collided with the earth . Our moon is the fifth largest satellite in the solar system . The moon has the largest mass proportional to its orbiting planet compared with moons of other planets . The tilt of the Earth is at 23.5 degrees , that is responsible for the different seasons we experience on the planet .   

 Mars was named after the roman god of war after its blood-like color. The planet is the nearest planet to earth after Venus. It has a diameter of 6794 km,approximately half as that of the earth , also one day on mars is very identical to that of the earth as it spins around its axis only in 24.62 hours . Mars has the biggest volcano named Olympus Mons in the solar system, it is 3 times higher than mount Everest. Mars rovers like spirit and curiosity have found signs of life on mars, In 2008 NASA confirmed the presence of water on Mars in the form of frozen ice beneath the surface . Mars is often called as the red planet because if its rust - red color. It has this color because of iron – oxide present in its soil. Almost all the water on Mars is frozen into ice. Mars has two moons namely Phobos and Deimos. Phobos was named after one of the horses that drew Mars chariot and Deimos was named after one of Mars companions. These moons were discovered by American astronomer Asaph Hall in 1877 Phobos has a diameter of 27 km and Deimos as a diameter of 15 km.    

Jupiter is the fifth planet from the sun , It was named after the king of the roman gods . It is the largest planet in the solar system . It is separated by the four terrestrial planets by the Asteroid belt . The planet Jupiter is the heaviest planet in the solar system , it is twice as heavy as all the planets put together . This gigantic planet is1,42.984 km across . The orbit of this planeet takes 11.86 years and varies between 740.9 to 815.7 million km . A great red spot is present on this planet , it is a huge swirl of red couds . The great red spot    measures more than 40,000 km across . Jupiter has 67 moons . The largest number of moons in the solar system .Among these the four largest moons of the planet jupiter are Ganymade ( the biggest ) , Callisto , Lo and Europa . They are also known as Galilean moons as they were discovered by the Italien astromer Galileo Galilea  .

Saturn is the fifth planet from the sun . It was named after the Greek titan Cronos , god of farming and father of Zeus/Jupiter . It is famous for its ring system . It is the least dense planet in the solar system and it is believed that Saturn would actually be able to float on water if there was a surface big enough to hold it . Saturn has 62 moons . Among them Titan is the biggest moon , it is the only moon to have a dense atmosphere . Saturn is the most faint planet to be visible from earth wihout a telescope . Saturn mainly two sets of rings the ‘A’ ring and the ‘B’ rings those rings are separated by the Cassini division . The rings may be fragments of a moon that was torn apart by the gravity of Saturn before it was formed properly . Saturn takes 29.46 years to travel around the sun . The plant is almost entirely made up of the gases hydrogen and helium and has solid rock only in its core . Despite of the gigantic size of the planet it rotates in just 10.66 hours .

Uranus is the seventh planet from the sun and it is named after the Greek god of the sky . The planet was discovered by the scientist William Herschel on March 13 , 1781 . Uranus has more than 20 moons , among them the biggest is Titania and the smallest is Trinculo . The moon of Uranus are named after the characters of Shakespear’s plays . Ariel , Umbriel , Oberon , Miranda are also its large moons . The planet takes 84 years to complete its orbit and is 2870 million km away from the sun at an average . Uranus is a very cold planet . The temperatures here drop to -210 degrees Celsius . Sunlight takes just 8.3 minutes to reach earth but 2.5 hours to reach Uranus .  Uranus is 52,118 km across and has a mass which is 14.54 times that of the earth . The atmosphere of Uranus is composed of Hydrogen and Helium . The planet is tilted so much that it seems to roll around sun , Its tilt is 98 degrees , thus its Equator runs vertically . The planet is very windy and winds travel at more than 600 km/h , about six times stronger than hurricanes on earth .   

Neptune is the eighth and the last planet of the solar system . It was named after the roman god of the sea .This planet was discovered in the year 1846 . Two mathematicians , Englishman John Couch Adams and Frenchman Urbain Le Varrier predicted the astronomers where the planet would be after the effect of the gravity of the planet Uranus on the planet . Neptune is the farthest planet from the sun , therefore its orbit is very long and lasts 164.79 earth years . Neptune is the windiest planet in the solar system with winds ripping across at more then 2000 km/h . The planet has has 14 known moons . Among them Triton and Nereid are the main ones and Triton is the biggest . Also the coldest known temperature in the solar system has been recorded on Triton with a surface temperature of -236 degrees Celsius . A great storm was observed by the voyager 2 spacecraft on the planet and therefore it was named the great dark spot , however now it has disappeared .    

  Pluto was discovered by the astronomer Clyde Tombaugh in the year 1930. From its discovery in 1930 till 2006 it was believed as planet, but after that its status was demoted to a dwarf planet. The Reasons were: ·

•  It was not big enough to be considered a planet.·
•  Its orbit was inclined too much from the ecliptic and had large eccentricity. · 
• It is a member of the Kuiper belt. 

The dwarf planet has a diameter of 2372 km. and an orbital period of 246 earth years. It was named after the Greek god Hades or the roman god of underworld. Also it has 5 moons, Charon, Styx, Nix, Hydra and Kerberos. With the largest one being Charon. The New Horizons mission was sent by NASA to Pluto in the year 2006 and it completed its flyby of Pluto on July 14 2015 .