Formation Of The Jovian Planets example essay topic

812 words
One of the most important areas of astronomy is the field of Comparative Planet ology. By studying planets and other large bodies in the solar system, we learn about the history and possible future of our own. There are nine planets in our solar system namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. These nine planets are classified into two groups: Jovian and Terrestrial, except for Pluto which is an entirely different system.

These planets were classified as Jovian and Terrestrial Because of the differences that these two types of planets have. Here is a chart of the differences between these two types of classification: Comparison of the Terrestrial and Jovian Planets Terrestrial Jovian close to Sun far from Sun closely spaced orbits widely spaced orbits small masses large masses small radii large radii predominantly rocky predominantly gaseous solid surface no solid surface high density low density slower rotation faster rotation weak magnetic fields strong magnetic fields no rings many rings few moons many moons Pluto is the farthest planet from the Sun and by far the smallest. Pluto is smaller than seven of the solar system's moons (the Moon, Io, Europa, Ganymede, Callisto, Titan and Triton). Pluto was discovered in 1930 by a fortunate accident. Calculations which later turned out to be in error had predicted a planet beyond Neptune, based on the motions of Uranus and Neptune. Not knowing of the error, Clyde W. Tombaugh at Lowell Observatory in Arizona did a very careful sky survey which turned up Pluto anyway.

Little is known about Pluto's atmosphere, but it probably consists primarily of nitrogen with some carbon monoxide and methane. It is extremely tenuous, the surface pressure being only a few micro bars. Pluto's atmosphere may exist as a gas only when Pluto is near its perihelion; for the majority of Pluto's long year, the atmospheric gases are frozen into ice. Near perihelion, it is likely that some of the atmosphere escapes to space perhaps even interacting with Charon. After the discovery of Pluto, it was quickly determined that Pluto was too small to account for the discrepancies in the orbits of the other planets and there are some who think Pluto would be better classified as a large asteroid or comet rather than as a planet. Some consider it to be the largest of the Kuiper Belt objects (also known as Trans-Neptunian Objects).

There is considerable merit to the latter position, but historically Pluto has been classified as a planet and it is very likely to remain so. We can actually determine the size of the planets through a series of formulas and by measuring the angular size of a particular planet. First, we need to convert an angular diameter into a physical one, measured in kilometers. If the angular size of an object is measured in radians, and if the object appears small in the sky, then its physical size is given by its distance multiplied by its angular size.

This relation is known as the small-angle formula and is very useful in determining the size of a planet. Terrestrial planets formed when space debris, mostly dust and rocks, constantly bombarding the young planets. This bombardment heated up the planets surface to the point where it began to melt, producing lava. Some of the original heat, though not enough to melt the planets interior, came from gravitational energy released as particles came together to form the terrestrial planets. It is known that all the terrestrial planets were made this way and therefore gave them the similarities in characteristics that they have. The Jovian Planets are mainly composed of gases just like our sun.

So with this, the formation of the Jovian Planets can be traced back to the solar nebula with fewer modifications than the terrestrial planets went through. Within the outer, cooler regions of the solar nebula, the icy planetesimals collided, building larger bodies of ice and rock. As these bodies grew to a mass a few times that of the Earth, then they drew in more hydrogen and helium from the surrounding interplanetary gas. Naturally, capture and retention of gas were easier far from the Sun, where the temperature was lower. Because of their great masses, they have kept very nearly the same relative proportion of hydrogen and helium to the heavier elements as the Sun and the interstellar medium have. This is the most likely mode of formation for Jupiter and Saturn and why they are hydrogen-rich bodies.

Uranus and Neptune were simply never massive enough to accrete hydrogen and helium to the extent that Jupiter and Saturn did. Thus carbon, nitrogen, oxygen, silicon, and iron dominate their compositions.