The Solar System

Our Solar System is currently made up of the Sun, nine known planets, as well as other space debris such as meteors, asteroids, moon, etc. All the planets and other orbiting bodies are held in their orbits as a result of the gravitational pull of the Sun. Approximately, 99% of the mass of our solar system is made up of the Sun. Its huge mass and gravitational pull is what makes it the controlling force in our solar system.

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The Sun:
Our sun has a diameter of about 1 400 000 km (110 times that of the Earth). In fact, you can fill in the Sun with about one million Earths. The Mass of the sun is 330 000 times that of the Earth. Quite fascinating considering it is made up of hydrogen and helium gases, the lightest known gases on Earth. That is why its density is only 1/4 that of the earth's. The Sun is made up several layers of gases, one blending into another. The core is what supplies the sun with its energy. The core can reach temperatures of 15 000 000 C. This high temperature is what allows the hydrogen atoms to fuse together to form helium atoms. In fact, the sun can convert about 4.5 million tons of hydrogen into energy every second. Not to worry since there is still enough hydrogen in the sun to last another 5 billion years.

The Sun is the central body in our solar system. It is a big ball of gas measuring about 1.4 million km in diameter. There is a lot of activity on the surface of the sun. We know that it is made up of four layers. They are:

	The Core
	The Photosphere
	The Chromosphere
	The Corona

The Core:
Most of the light and heat is produced in the core. Here, nuclear fusion takes place. In nuclear fusion, two hydrogen atoms are fused together to form one helium atom. This reaction releases a tremendous amount of energy. The temperatures in the core can reach as high as 15 million degrees Celsius. A helium atom is twice as heavy as hydrogen making the core dense as more hydrogen undergoes nuclear fusion. Eventually, the core will convert all of the hydrogen into helium thus becoming heavier, more dense, and cooler. Presently, our sun is about middle-aged and not too hot or too cool for a star. The energy produced in the core makes its way to the next layer of the sun by radiation.

The Photosphere:
In the Photosphere, the energy moves around through the process called convection. It is in this layer that we get most of the sun's radiant (light) energy. Its average temperature may reach as high as 5500 degrees Celsius. It is in this layer as well that the cooler areas form what is known as Sun Spots.

The Chromosphere:
This layer forms the inner layer of the sun's atmosphere.

The Corona:
The Corona forms the hotter outer layer of the sun. Temperatures in this layer may reach as high as 1 million degrees Celsius. This is the layer that is visible during a solar eclipse. This layer can extend for several million km. It is made up of very thin gas that streams out in thin flat layers due to the effect of the Sun's magnetism.

Activities on the Sun's Surface may include any one of the following phenomena:

	Solar Flares
	Solar Prominence
	Sunspots
	Solar Wind

Solar Flares are described as violent explosions that occur normally over sunspots. They last only for a few minutes, but their effects can be felt by the Earth's magnetic field. Solar flares are also responsible for the formation of solar winds.

Solar Prominence describes streams of flames that jet out from the surface of the sun. They are often described as solar storms. They appear as huge loops of flames that take several hours before returning to the surface of the sun. They can be seen during an eclipse.

Sunspots are darker cooler areas on the surface of the sun. They are normally found near areas of solar flare activity. Upon closer inspection, astronomers have observed clouds of glowing hydrogen gas jets appearing around these sunspots. The frequency of sunspot activity usually occurs in cycles of approximately 11 years.

Solar Wind is caused by the release of particles from the sun. These particles are made up of charged atomic particles that affect the planets' magnetic fields by distorting their overall shapes.

The Nine Planets:
The nine known planets in our solar system consist of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. The first four make up the inner planets. They have the similar characteristic of having been made up of primarily solid substances. The remaining planet are called the outer planets and are primarily made up of gases.

Other Orbiting Bodies:

Asteroids -Most of these are generally located between the orbits of Mars and Jupiter. Most have a diameter of 1 km or less, however, there are a few that are the size of a small moon. There has been a reported case of one having a diameter of about 955 km. Asteroids seem to be the leftover pieces from the larger parts when the solar system was being formed. There seems to be a growing concern of some of these larger asteroids making their way into the Earth's orbit. The possibilities of them hitting the Earth is very much real. In fact, it is believed that the cause of the recent ice age was a result of the earth's collision with one of these asteroids. As a result, astronomers have become even more vigilant of what celestial bodies may be making its way towards the Earth

Meteorites and Meteors - Many of the smaller celestial debris in our solar system do collide with each other and other planets, meteors, asteroids, etc. Most of these meteors are very small and have a mass of less than 1 gram. They move very fast. When they travel through the Earth's atmosphere, the friction between the air molecules and the rock surface causes these pieces to burn up, in most cases, before they hit the ground. This friction is what causes the bright streaks of light that one sees during the night sky. They are often referred to as Shooting Stars. Meteor showers are most likely to occur during early May, mid August, and mid to late October. They are heaviest after midnight.

Some pieces may be large enough to make it to the Earth' surface. These fallen objects are called meteorites. They can be identified by the heat marks left on the surface of the rock as a result of the friction between the atmosphere and the rock's surface. About 90% of meteorites found are made up of the same rock materials one would find on the Earth's surface. Other meteorites are made up of mainly iron with a small amount of nickel.

Comets - Billions of these celestial bodies are believed to be traveling around the edges of our solar system. Every once in a while, one of them manages to visit us. Comets are basically celestial snowballs that travel through space in an orbit around the Sun. They can vary in diameter from a few meters to about 100 km.

Once a comet manages to travel inside Jupiter's orbit, the Sun's energy will begin to turn some of its icy material into a gas that seems to trail away from it. Because of the Comet's motion, one will notice that the this tail of gases always seems to be pointing away from the sun. Some comets will actually begin to break apart as they travel closer to the sun. Others will make several trips in its lifetime. Eventually, it will lose some material each time until nothing remains. The most famous Comet, Halley's comet, seems to visit us every 76 years. It was last seen in 1986.