OUR SOLAR SYSTEM
We as inhabitants of Earth are an integral part of the Solar System. Its study can explain why and how Earth is our home, while the other planets are not. The Solar System was formed when a huge cloud of gas condensed millions of years ago and formed solid objects. They gradually joined to form the Sun and the nine planets around it. At the time of its birth, most of the gas got driven away from the Sun because of its intense heat and vaporized.
This led to the heavy metal elements to settle near the Sun and form the four rocky inner planets of Mercury, Venus, Earth and Mars, while the outer planets of Jupiter, Saturn, Uranus and Neptune emerged as huge gas bodies. Lying between the inner and the outer planets is an asteroid belt, which is said to consist of many asteroids orbiting the Sun. The discovery of little Pluto, which is not really considered a planet of its own, led many scientists to believe that many more celestial bodies of the kind were waiting to be discovered in the future. Pluto is found on another belt of objects known as the Kuiper Belt Object that is located outside the orbit of Neptune.
The four heavier inner planets are rocky, denser and have very little atmosphere. In fact, Mars and Mercury hardly have any atmosphere. Whereas the outer four planets have huge dimensions made up of accumulated gas. These outer planets get very little light and heat from the Sun since they are at a great distance from the Sun. It is interesting to note that Sun isn’t the only source, of light and heat for the planets; in fact, they all give out some energy of their own.
The terrestrial ones emit heat owing to the slow radioactive decay of isotopes that were formed since the birth of the system, while the gas planets give out heat that was left over during the planets’ final stages of contraction at the time of their formation. The outer planets emit more heat than the inner planets with the exception of Uranus.
Of the four inner planets, Mercury and Mars are both small and are almost devoid of any atmosphere. Mercury has a diameter of 4,800 km while Mars is slightly larger with a 6,700 km diameter. Both the planets are smaller to Earth, which has a diameter 12,800 km. The other two inner planets Venus and Earth are almost identical in their size, composition, mass and density.
However despite their similarity, Venus is very unpleasant for inhabitation due to its close proximity with the Sun. Its atmosphere is stifling and extremely hot, where as Earth by virtue of being located at a comfortable distance from Sun is more supportive of human lives.
Talking about the outer planets, Saturn and Jupiter are both colossal with their diameters measuring 120,000 km and 142,000 km respectively. The other two outer planets of Uranus and Neptune are much smaller and can easily fit inside the core of the first two giants. The diameters of Uranus and Neptune are 51,800 km and 50,000 km respectively.
The reason for this large disparity in their sizes is due to the fact that the first two giant planets have very high internal pressures that cause large quantities of Hydrogen into a metallic state in their cores, whereas Uranus and Neptune produce only a small portion of this amount. Electrical currents moving through the metallic state of Hydrogen generate large magnetic fields in Saturn and Jupiter. Whereas the magnetic fields in Uranus are much smaller.
As generally perceived, the solar system does not end with Pluto. Another belt of objects that is orbiting the Sun exists and it is not only larger in area but also has a much greater mass than the asteroid belt, we know of. This belt, known as the Kuiper Belt, was found in 1980s and is estimated to be 150,000 million kilometers from the Sun! Pluto is thought to be an object of this belt and not really a planet by many astronomers. Though we have learnt a lot about the solar system through space exploration, looking at its expanse and reach we have yet to learn a lot.