What Are The Planets Made Up Of?

The IAU (International Astronomical Union), held a debate in 2006, in which more than 2500 astronomers from throughout the world participated and they agreed on calling a body a planet if it satisfied the following conditions:

(1) The body is orbiting the sun

(2) It should have sufficient mass to be in a round shape

(3) It should have ‘cleared the neighborhood’

Cleared the neighborhood means there are no other celestial bodies of comparable size in the neighborhood of the planet. In our solar system, Pluto couldn’t fit in the new definition so it was left out. Now there are eight planets in our solar systems and their compositions differ. Some are gaseous, like Jupiter while others are rocky, like our own planet. Let’s see how planets are formed and later we will look at our own planets.

The most widely believed theory is: a rotating cloud of gas in the universe begins to contract because of gravity. Soon (here the word soon means in course of millions of years) the density at the center of the cloud begins to rise. And because of this density the center begins to heat up. It heats up so much, that the atoms of hydrogen which are prevalent in the gas, start fusing, thus a star is born. Not all of the gas is consumed up when the star is formed; this results in a residue rotating around the newly formed star. In the course of time, that residue of gases and other materials begin accumulating (again the cause is gravity) and planets are formed in time.

Let’s come back to our own solar system and see what our planets constitute of:

Mercury: This first planet from the Sun has a dense iron core at the centre and the mantle and crust are of silicate materials. Because of its proximity to the sun, the planet has lost the atmosphere it once had.

Venus: Nickel and iron constitute the interior of this planet, but it is still a controversial issue. It has been proved by experiments that carbon dioxide makes up its atmosphere.

Earth: Back home, we have found that 30% of the centre of our planet (core) is iron. There is also 30% oxygen present in various compounds and magnesium with accounts for 14% of the earth’s mass.

Mars: This god of war to the Romans is also the most famous of all planets. There is 16% sulfur present is its core and the silicate materials form the mantle.

Jupiter: This planet is considered as the great teacher in Hindu mythology. It is the largest planet in our solar system. This is a gaseous planet but it is suspected that the planet has a rocky core at the center with is enclosed by a sea of liquid hydrogen. Jupiter is 90% hydrogen.

Saturn: It is the second largest planet in our solar system and has got almost the same composition but Saturn in hotter than Jupiter at its center. It has been proved by the amount of energy it radiates. It radiates more energy than it gets from the sun.

Uranus: Rocks and ice form this planet. Ice on Uranus is formed by a mixture of water, ammonia and methane, thus it is different from water ice we normally encounter in our freezers. Again, hydrogen makes up 83% of its atmosphere.

Neptune: This is the farthest planet from the sun and hydrogen and makes up nearly 15% of this planet. The rest is rocks and ice.

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