Solar System

Solar System
About 4,700 million years ago, the Solar System was just a spinning disc of dust and gas. The dust began to collect together and our Sun formed at the centre.
Around Sun, lumps of rock joined up to form smaller bodies and, like the Sun, they heated up. But because they were smaller they soon cooled down and became planets. Sun accounts for 99.85 per cent of mass of the solar system. About 1.3 billion earths would fit inside the sun.
The solar system consists of the Sun; the nine planets, 67 satellites of the planets and a large number of small bodies (comets and asteroids). The inner solar system contains the Sun, Mercury, Venus, Earth and Mars. The planets of the outer solar system are Jupiter, Saturn, Uranus and Neptune.
Mercury –
Mercury is named after the messenger of the Roman gods. It is the smallest of the inner planets and the second smallest in the whole Solar System. It has a very weak magnetic field and – being the closest planet to the Sun – has only a very thin atmosphere of helium captured from the solar wind.
Venus –
Venus is named after the Roman goddess of love. It is the second planet from the Sun and the brightest object in the sky other than the Sun and the Moort. Venus has the most hostile environment in the entire Solar System. The surface temperature is fiercely hot and the atmospheric pressure is crushing. One of the more apparent things that separate Venus from all the other planets in our solar system is that it rotates from east to west (all the other planets rotate from west to east).
Earth –
The Earth, the third planet (rock) from the Sun, is the largest of the inner planets and also has the highest density. It is the only planet in the Solar System to be covered largely with water, the only planet with an atmosphere made up chiefly of nitrogen and oxygen and the only body that has a temperature suitable for life of the type that we know.
The Earth’s rotation period is not constant. It is slowly lengthening due to tidal friction between the oceans and the sea floor. This is caused by the influence of the Moon.
Mars –
Mars is the fourth planet from the Sun and the seventh largest. It is sometimes referred to as the Red Planet. The name of the month March derives from Mars. Mars has been known since prehistoric times. Except for Earth, Mars has the most highly varied and interesting terrain of any of the terrestrial planets.
Jupiter –
Jupiter is named after the king of the Roman gods. It is the largest planet in the Solar System. Jupiter has a magnetic field 20,000 times stronger than that of the Earth’s, having a devastating effect on its moons.
Saturn –
Saturn is the sixth planet from the Sun and the second largest: In Roman mythology, Saturn is the god of agriculture.Galileo was the first to observe it with a telescope in 1610. Saturn is about 75% hydrogen and 25% helium with traces of water, methane, ammonia and rock.
Uranus –
Uranus is the forth largest planet in the Solar System and the seventh from the Sun. Named after the father of Saturn. It is a blue-green colour due to the methane in its atmosphere.Uranus is composed primarily of rock and various ices, with only about 15% hydrogen and a little helium.
Neptune –
Neptune is named after the Roman god of the sea. It is the third largest planet in the Solar System and is usually the second last planet in distance.
Because of Pluto’s eccentric orbit, Neptune is the last planet for 20 years every 247 years.
Pluto –
Pluto was discovered on February 18, 1930, making it the last planet found in our Solar System. Pluto is usually farther from the Sun then any of the nine planets. Ground-based observations indicate that Pluto’s surface is covered with methane ice and that there is a thin atmosphere that might freeze and fall to the surface as the planet moves away from the Sun. Pluto has one moon – Charon
On August 24, 2006, the International Astronomical Union (IAU) formally downgraded Pluto from an official planet to a dwarf planet.
According to the new rules, a planet meets three criteria: it must orbit the Sun, it must be big enough for gravity to squash it into a round ball, and it must have cleared other things out of the way in its orbital neighborhood.
Asteroids –
Asteroids are rocky and metallic objects that orbit the Sun but are too small to be considered planets. They are known as minor planets. Asteroids range in size from Ceres, which has a diameter of about 1000 km, down to the size of pebbles. Sixteen asteroids have a diameter of 240 km or greater.
Meteors and Meteorites –
The term meteor comes from the Greek ‘meteoron’, meaning phenomenon in the sky. A meteoroid is matter revolving around the sun or any object in interplanetary space that is too small to be called an asteroid or a comet. A meteorite is a meteoroid that reaches the surface of the Earth without being completely vaporised. Meteorites have proven difficult to classify, but the three broadest groupings are stony, stony iron, and iron. The most common meteorites are chondrites.
Comets –
Comets are small, fragile, irregularly shaped bodies composed of a mixture of non-volatile grains and frozen gases. They have highly elliptical orbits that bring them very close to the Sun and swing them deeply into space, often beyond the orbit of Pluto. Comet structures are diverse and very dynamic, but they all develop a surrounding cloud of diffuse material, called a coma, that usually grows in size and brightness as the comet approaches the Sun. As comets approach the Sun they develop enormous tails of luminous material that extend for millions of kilometers from the head, away from the Sun.
Conclusion
Astronomy usually began with the Greeks. Nicolaus Copernicus, in 1543, published his hypothesis that the Sun is the center of the universe. Five years after the appearance of the great supernova of 1604, Galileo built his first telescope. At the age of 23, young Isaac Newton realised that gravitational force accounts for falling bodies on earth as well as the motion of the moon and the planets in orbit. This was a revolutionary step in the history of thought in the solar system. Einstein’s General Theory of Relativity replaced Newton’s model of gravity with one in which the gravitational force is interpreted as the response of bodies to distortions in space- time which matter itself creates.
Various improvements have been seen in the study of the Solar system over the past few centuries. They have proved better for the mankind in many ways.