ASTROGEOLOGY 1 (ORDINARY LEVEL)

INTRODUCTION TO THE UNIVERSE

            The universe as used in geology, is a general term for all existing things; that is the whole creation including all heavenly or celestial bodies, and all the space whether known to man or not.

The solar system and the stars are members of the universe. The earth is a member of the solar system whose centre is the sun around which all other members revolve. The small stars we see in the sky at night are surprisingly far much bigger than the earth.

Many millions of Stars tend combine to form groups or clusters known as galaxies. The solar system and including the earth belong to the Milky Way galaxy.  There are many other million galaxies in the universe and the nearest galaxy to the earth visible to the naked eye is the Andromeda. 

 

Figure 1: The Milky Way galaxy (Our Galaxy)

THE SOLAR SYSTEM

            The solar system is made up of the sun and eight planets which revolve around it in elliptical orbits.  also revolving around the sun are comets and meteorites. 

            The planets are, in order from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Pluto, which was known for a long time as the ninth planet, is now called a dwarf planet.  The nearest planet to the sun is mercury while Pluto is the farthest. It is about 5.9 billion miles away from the sun.

The first four planets from the sun;. Mercury and Venus, Earth and Mars are called inner planets or terrestrial planets.

And those after Mars, that is Jupiter, Saturn, Uranus, Neptune and Pluto are called the outer planets or Jovian planets.

 

Figure 2: The solar system showing the relative positions of the eight planets

Positions of the Planets in The Solar System

	PLANETS	Approximate Distances from the Sun (in millions of kilometers)
1.	Mercury	57.9 million kilometers
2.	Venus	108.2 million kilometers
3.	Earth	149.6 million kilometers
4.	Mars	228 million kilometers
5.	Jupiter	778.4 million kilometers
6.	Saturn	1424.6 million kilometers
7.	Uranus	2873.5 million kilometers
8.	Neptune	4501 million kilometers

Table 1: Positions and distances of the planets of the solar system