The Solar System
The Sun appears to have been formed 4.9 billion year ago. Many stars appeared before this and many more appeared before the formation of the sun. This seems to be an unending process. The Solar System Consists of the sun and the objects that orbit in the system comprise one star, The sun, eight planets and their moons. It also consists thousands of asteroids/planetoids and numerous comets.
The inner Solar System includes the four terrestrial planets and the asteroid belt where as the outer solar system is beyond the asteroids. The outermost parts of the solar system are considered a distinct region consisting of the objects beyond the planet Neptune.
In order of their distance from the sun, the planets of the Solar system are: Mercury, Venus, Earth, mars, Jupiter, Saturn, Uranus and Neptune. The inner Solar System refers to the region comprising the terrestrial planets and asteroids. The objects of the inner solar system are relatively close to the Sun. The four inner or Terrestrial planets have rocky composition with few or no moons and without any ring system. They are composed of Silicates (Crusts and mantles) and metals such as Iron and nickel (cores). Out of these four planets Venus, Earth and Mars have atmospheres and tectonic surface features.
All Planets rotate upon their axis-Venus and Uranus – from east to west and all other planets, from west to east. The direction of planets in their revolution around the sun is also from west to east.
The temperature found on each planet depends upon its distance from the sun. More the closeness, high is the temperature.
Every member of the Solar System revolves round the Sun. It is the only source of heat and light for the entire solar system as it is made up of extremely hto gases. The sun provides the entire energy sustaining the living beings. It rotates on its axis in 25 days 9 hours and 7 minutes. Its rays travel at a tremendous speed of about 300,000 Kmps and take a little more than 8 minutes to reach the earth. It is rather large and bright when compared to the majority of stars in the Milky Way.
Scientists believe that the solar system has been formed out of the solar nebula - a giant, rotating cloud of gas and dust. The nebula spun faster and flattened into a disk as it collapsed due to its gravity. Those materials which pulled towards the centre formed the sun where as the asteroids, comets, moons and planets were formed due to the combination of asteroid – sized objects.
Mercury : It is the smallest of the eight planets orbiting the sun. It is also the closest planet to the sun. Although closest to the sun, it has the largest range of temperature change from day to night. It is believed to be airless and waterless planet. It has no moon but has an atmosphere and a weak magnetic field.
Venues : It is the brightest of all the planets and is slightly smaller than the earth. It is frequently referred to as the Morning star or the Evening star as it is often visible in the morning and evenings. Contrary to the spin of other Planets, it rotates very slowly in a clockwise direction. It is the third brightest object in the sky next. To the Sun and the Moon and can be easily visible with naked eye.
The Earth : It is the fifth largest planet in the solar system and lies between Venus and mars. It orbits round the sun and takes 365 days, 5 hours, 48 minutes and 45.51 seconds to make one revolution. It takes 23 hours, 56 minutes and 4.091 seconds to complete one rotation on its axis.
The Earth has only one natural Satellite (The moon). It is the only planet with adequate water and air around it. Its temperature is also very suitable for flora, fauna, aquatic and human life.
Mars : This planet is named after the Roman god of war as its distinct red colour as seen from the earth reminded the people of blood. It takes about 687 days to complete one revolution around the sun. It takes 24 hours, 37 minutes and 22.633 second to rotate on its own axis. It has two satellites- Phobos and Deimos. In July 2000, NASA announced the evidence of water on Mars which created a new era in the search for life on this planet.
Jupiter : It is the largest planet of our solar system. It is basically a gaseous planet composed of hydrogen and hydrogen compounds. It takes 4,332.62 day (about 12 years) to complete one revolution around the sun. It has also a ring system like Saturn but not visible from the Earth. It has at least 64 satellites This Planet is greatly flattened at the pole due to its rotation at a very high speed.
Saturn : This planet looks like a bright star. The rings can be seen with a small telescope. It takes about 30 years to complete one revolution round the Sun. It takes 10 hours and 14 minutes to complete one rotation on its axis. This Planet is circled by at least 62 satellites. Its satellite Titan is the only satellite in the solar system to have clouds and a dense atmosphere composed mostly of nitrogen and methane scientists believe that the Titan rocks may harbor life in their pores.
Uranus : It is the seventh planet from the sun. It takes about 84 years to revolve round the sun. It takes about 16 hours and 10 minutes to rotate on its axis. It goes round the sun nearly lying on its side as its axis is tilted at 97 degrees. It has at least 27 satellites. Titania (1580 km) and Oberon (1516 km) are its two largest satellites.
98% of the upper atmosphere of Uranus is composed of hydrogen and helium. The renaming 2% is composed of methane.
Neptune : It is the eight planet in the solar system. It takes nearly 165 years to make a revolution round the sun. it takes about 18 hours and 26 minutes to rotate on its own axis. It has at least 13 natural satellites Pluto is no longer a planet because of its oblong orbit which sends it soaring above and beyond the main plane of the solar system where the other eight planets circle the sun.
As per International astronomical union criteria Pluto has been placed under the category of a dwarf planet along with Xena and Ceres. Thus the number of plants has come down to eight from the previous nine.
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