ASTROGEOLOGY (PLANETARY GEOLOGY)
This is the
scientific study of planetary surfaces, employing the techniques of geology. It involves Astronomy which is the scientific study of the universe, especially
of the motions, positions, sizes, composition, and behaviour of astronomical
objects.
Since the
earth is an integral part of the universe and is one of the celestial bodies,
therefore, Astrogeology includes the
study of the earth as part of the universe.
INTRODUCTION TO THE UNIVERSE
The universe is an embracing term
for an aggregate of all existing things; that is the whole creation including
all heavenly or celestial bodies, and all the space whether known to man or not.
It is the totality of space and time, past, present and future, consisting of
millions of stars clustered in galaxies.
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. Astronomers have calculated that despite the billions of stars scattered
throughout the universe, they occupy only a small volume of the universe if put
together.
Stars tend
to form clusters known as galaxies. The solar system and hence
the earth belong to the Milky Way galaxy. The Milky Way
galaxy is spiral in shape and rotates slowly in space, completing one rotation
in about 240 million years. There are many other million galaxies in the
universe and the nearest galaxy to the earth visible with the unaided eye is
the Andromeda. The distance of the Andromeda from the earth is estimated
at 2.54 million light years. A light year is 1013km. It is the
distance light travels in one year. Our galaxy has a diameter of 100,000 light
years.
Figure 1: The Milky Way galaxy (Our Galaxy)
THE SOLAR SYSTEM
The solar system consists of the sun and [1]eight
planets which revolve around it in elliptical orbits. also
revolving around the sun are comets and meteorites. The space in the solar system between the
members consists of a mixture of dust and gas.
Some of the planets have satellites around them for example; the moon is
satellite of the earth. At the centre of
the solar system is the sun which is a gaseous body consisting of burning
hydrogen and helium with much smaller quantities of heavier elements including
oxygen, carbon, neon and iron. The sun
has a diameter of 864000 miles and has temperatures up to 55000oc at
its surface.
The planets are, in order from the Sun: Mercury, Venus,
Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto, 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 planets between the earth’s orbit and the sun;. Mercury and Venus,
including Mars resemble the Earth and are made entirely of magnesium and
silicates. They are called inner
planets terrestrial planets and those beyond Mars, that is Jupiter,
Saturn,
Uranus,
Neptune
and Pluto
are made up mostly of hydrogen and helium which are light gases and 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
|
DISTANCE FROM SUN
(millions of kilometers)
|
SOLAR DIAMETER (miles)
|
DENSITY
|
NO
STATELITE
|
|
Mercury
|
57.9
|
300
|
5.9
|
0
|
|
Venus
|
108.2
|
7600
|
5.16
|
0
|
|
Earth
|
149.6
|
7900
|
5.25
|
1
|
|
Mars
|
228
|
4200
|
1.89
|
2
|
|
Jupiter
|
778.4
|
88000
|
1.29
|
12
|
|
Saturn
|
1424.6
|
75000
|
0.62
|
10
|
|
Uranus
|
2873.5
|
29300
|
0.6
|
5
|
|
Neptune
|
4501
|
27700
|
2.21
|
2
|
|
Pluto
|
5945.9
|
8700
|
4.2
|
0
|
Table 1: Positions and distances of the planets of
the solar system
Web Sources:
No comments:
Post a Comment