The Quick Guide to the Universe

We live on a planet called the Earth, a beautiful water and rock-covered globe about 8000 miles in diameter, travelling through space in orbit around the Sun, spinning all the while on its axis.

Our Sun is a star and the source of all life on Earth - we would perish without its radiation. It is a nuclear fireball about one hundred times the diameter of the Earth, constantly burning hydrogen gas as its fuel. The Sun has been shining for about five billion years, and is about half way through its life.

The solar system is the general name for the Sun and its family of planets, all of which formed out of the same cloud of gas and dust all those aeons ago. But every star we see in the sky is also a 'sun' - home to other planets we are only just beginning to discover.

Stars live from between millions to trillions of years, existing in the same state of nuclear burning, and seen from a distance as a pinpoint of light. But as a star starts to die, it throws off layers of gas, which then glow in the light the star is still emitting. These are called planetary nebulae (see picture of the Helix nebula on the right) and make up some of the most beautiful and exotic objects in the galaxy.

Stars are the building blocks of the Universe, in the sense that they create the light - they bring it to life. But stars do not just wander freely through the cosmos. They are found in vast groups - 'islands' in space called galaxies, which contain up to hundreds of billions, even trillions of stars.

All the stars we see in our sky are part of the spiral galaxy we belong to, known as the Milky Way, and the Sun is placed about two-thirds of the distance out from the centre. Distances in space are so huge that they are measured in the time it takes light to travel, and so to compare: it takes light eight minutes to travel from the Sun, four years to travel from the nearest star, and one hundred thousand years (at least) to travel across our galaxy.

Galaxies can be seen in various shapes and sizes, and at various stages of evolution - some can even be seen to be merging together, pulled together by gravity. Looking across the great expanse of space, enormous clusters and super-clusters of galaxies can be seen, forming patterns like spiders webs across the Universe.

But scientists can see that the space between clusters, between galaxies is growing, and they currently believe that all space is expanding as a result of the formation of the Universe in a Big Bang.

By looking at the faintest objects, they can look back in time, seeing the earliest galaxies and stars that formed in the Universe, those cosmic lights which have travelled through the expanding space for billions of years to reach us today. The history of the Universe is pouring onto the Earth for us to ponder, and capture through our telescopes, and our essences.