The small rock we live on, that we call the Earth, orbits a star - our sun, at a distance of 149,598,000 kilometers. The next closest star system to our solar system is Proxima Centauri which is at 4.33 light years, not the commonly noted Alpha Centauri. The two are infact part of the Alpha Centauri triple star system, the third is Beta Centauri.

The light year is a measure of distance often used in astronomy because of how large it is. One light year is the distance that light can travel in one year and at 3x10^8 meters per second, it gets 9.46x10^14 meters in a year! If you are unfamilar with this form 10^3 is a one followed by three zeros, so the light year is 946 followed by fourteen zeros! This notation is useful in astronomy as it saves alot of time and space when writing such large numbers.

Our sun is just one of 200 billion stars in the Milky Way galaxy. The Milky Way is a fairly large spiral galaxy that is approx 30,000 parsecs in diameter - the parsec is another unit of distance used in astronomy, it is defined as the distance from which an observer would see one astronomical unit subtend one second of arc (a second of arc is 1/3600th of a degree). As illistrated below:

One parsec is equal to 3.1x10^16 meters or 3.26 light years. Using this simple conversion the Milky Way is around 100,000 light years or 1.85 billion trillion meters from one side to the other! Taking a step back, our Milky Way is only one of a group of galaxies we call the Local Group. The Local group is a cluster that consists of 30+ galaxies including Andromeda (M31), The Whirlpool galaxy (M110) and the small and large Magellanic clouds, just to name a few. Taking a further step back, there our thousands of these galaxy clusters outside our own Local group. One of these is the Fornax cluster which is found in the constellation of Fornax (click above pic for enlargement).

If we continue to step back the Local group is in turn part of what is deemed a super cluster of galaxy clusters and as far as we know there are hundreds upon thousands of super clusters... As you can see the the universe is a big place, and it would be an awfull waste of space if we where the only ones in it. That argument I will save for another guide.

Jayden Newstead