The Solar System
The solar system consists of various heavenly objects as planets, satellites, asteroids and comets revolving around the sun. The sun is just one of the innumerable stars of the Universe. Many such stars are known to have such systems of heavenly objects revolving around them. But we have so far been able to know more only about the solar system since our Earth is also a part of it.
Planets & Satellites:
Planets are huge heavenly objects which revolve around some or the other star. Planets donâ€™t have their own light as do the stars. Satellites are relatively smaller heavenly bodies which revolve around some or the other planet. Moon is the satellite of our planet, the Earth. Like planets, the satellites too donâ€™t produce their own light. Satellites only reflect the light of the stars at the center of their systems as our moon reflects the light of the sun.
Asteroids & Comets:
Asteroids are huge pieces of flying rocks that measure from a few feet to miles in diameter. Ceres (590 miles) is considered as the biggest asteroid. There are thousands of asteroids forming an asteroid belt between Mars and Jupiter. Comets are balls of rock and ice which grow a glowing tail as they near the Sun in the course of their journey around it. As comets heat up, the throw out gas and heat which results in the glowing tails behind them. The glowing tails of comets are sometimes visible from earth, in night sky.
The age of the Sun is estimated to be over 5 billion years. The Sun is a huge object consisting of almost 98% of the matter found in the solar system. The sun is composed mainly of hydrogen and helium. The powerful gravitational force of the sun pulls all the objects of the system towards it. At the same time the emptiness of the space around tries to suck in the objects into it. Caught between these two forces acting from opposite directions, the objects, including our Earth, keep constantly revolving around the sun in fixed paths. The almost circular and fixed paths in which these astronomical bodies travel are known as orbits.
Planets of the Solar System:
The solar system consists mainly of eight major planets including our Earth. The eight major planets in order of their nearness to the sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Mercury is the smallest planet of the solar system. It is the only planet without a satellite or a moon. Jupiter is the largest planet of the solar system. It has 14 satellites revolving around it. Saturn is well known for its system of rings surrounding it. It is the only outer planet visible to the naked eye, from earth. Saturn has 10 satellites. Venus is the planet closest to the Earth. Seen from the Earth, it the third brightest object in the sky after the sun and the moon. Venus is known as the evening star as well as the morning star. Beyond Neptune, we have another interesting object called Pluto. It is smaller than some of the satellites of the solar system. Until 2006, Pluto was also considered as a planet, as the ninth of our solar system. But because of its small size, scientists have now included it in a newly formed category of small planets called Pluto-ids.