Now the dark nights are back I thought it might be a good time to go back to basics and take a look at what stars actually are. People have all sorts of funny ideas about stars. Some think they are balls of fire hanging above us in the atmosphere. Others think they are pieces of rock out in space reflecting the sun's light. But the truth is even more incredible.

You see, our sun - you know, that brilliant ball of orange-yellow light which appears in the sky above Kendal once every week or so - is a star, the nearest star to the earth. It is a blazing ball of gas, a naked nuclear fusion reactor out in space, surrounded by a family of nine planets (or is it ten? The jury's still out on that one), of which earth is one.

All the stars you see after the sun has set are also suns - immense globes of incandescent gas - but they are so far away that they just look like tiny pin-pricks of light to us here on earth. This means that if you jumped into your starship and flew away from the sun you would see it shrink from a big bright ball to a tiny speck of light, until it looked like just another star, too.

And here's a brain-aching thought... if there are aliens out there in space, they see our sun as just a tiny star, twinkling in their night sky after their own sun has set!

You might think that all the stars are the same distance away from us - after all, they do look rather like dots of luminous paint spotted on the inside of a spherical shell surrounding the earth. In fact, the stars are all different distances away from us, so when you look up you're actually looking out into an endless ocean of blackness, where stars shine like tiny islands of light in the ink-black void. Space isn't up above us, it's out there, all around us, stretching off to infinity.

And how far away are the stars? Well now, there's a question. Space, the Universe, whatever you want to call it, is so huge that using kilometres to describe distances between objects in it is ridiculous, as ridiculous as using millimetres to describe the distances between cities, or hours to describe the time you need to find a parking space in Kendal. Instead, astronomers use light years as their unit of distance.

How many stars are there? Well, on a clear night we can see roughly 3,000 with our naked eyes. The sun is, though, just one star in a huge spiral cloud of 200,000 million stars called the Milky Way Galaxy. And for every one of the Milky Way's 200 billion stars, there's another galaxy out there, with as many stars of its own how small do you feel now?

As for why stars are different colours, that's because a star's colour tells us how hot it is. Blue stars are very hot 10,000 deg C + - while red ones are (comparatively) cool. Our sun's surface temperature of 6,000 degrees C is pretty average, which is why it is a middle-of-the-road orange yellow colour.

A closing thought - we now know of almost 200 stars with their own systems of worlds, and although none of these "extrasolar planets" is anything like the earth, it's just a matter of time until we find one, if not dozens of alien earths' out there, with their own oceans, continents and life.

So, next time the night sky's clear above South Lakeland and Furness, and you look up at the stars, smile there might be a telescope on an alien world staring right at you from across the gulf of space.