The conflagration at the heart of our solar system is a star named Sol. It is a star like all the other stars in the night sky, except that it's a lot closer, and a lot more important, at least to us. It holds our solar system together, and gives it the sustenance of life. Without Sol, there would be no solar system, no Earth, and no us.

The life of a star...

All stars begin as immense clouds of gas and dust. When one of these clouds is large enough, gravity begins to pull it together. As the cloud condenses it begins to heat up. After a few million years, the cloud has contracted into a compact ball of gas, and the temperature at its centre is hot enough to fuse hydrogen atoms into helium atoms, a process known as nuclear fusion, the same process involved with hydrogen bombs, and as we saw at Hiroshima and Nagasaki, it is a process that releases staggering amounts of energy. When the outward energy of nuclear fusion is strong enough to stop the inward energy of gravity, a precarious balance is reached between the two most powerful known forces in the universe, and a star is born.

For the next few billion years, the star continues happily burning away as a white hot young star, fusing hydrogen into helium, like millions of nuclear bombs going off simultaneously, over and over. But eventually, the star begins to run out of hydrogen. It begins to cool and change its colour to yellow. And as the outward pressure produced by fusion lessens, gravity begins to get the upper hand again, and the star begins to contract again. This compresses the helium in the centre of the star to the point where it begins to fuse into heavier, more complex elements. This is where all the complex elements in the universe come from. All the complex atoms that make up all the planets and moons and rocks and trees and you and me - were made inside stars.

This new fusion of helium into heavier elements creates a new outward energy that slowly overpowers the inward pull of gravity, and the star begins to expand, becoming a red giant. Finally, the star runs out of helium, and in a process not entirely understood, ends its life in the mother of all explosions: a supernova. This enormous explosion spews forth all the new elements formed by the star such as carbon, oxygen, nitrogen, magnesium, copper, gold and lead - to name a few - seeding the cosmos with the stuff of life.

Our Sun is approximately five billion years old, halfway through its life, so we don't have to worry about it exploding for another five billion years.

The classification of stars is illustrated by the H-R diagram below, named for the two astronomers, Hertzsprung and Russell, who designed it. Each star is given a letter, designating its spectral class, followed by a number from 1 to 9, specifying where it falls within that class. Our Sun is a G2 yellow main sequence star. It has a surface temperature of 6,000 degrees centigrade. In the centre of the Sun, the temperature is an unbelievable one million degrees!

The Sun is one million miles in diameter. A million Earths could fit inside it, with room to spare. It is 93 million miles away from us, a distance also known as one astronomical unit, one more tool to try and make sense of the vast distances in space. The Sun is so far away that its light - travelling 186,000 miles per second, takes a full eight minutes to reach us.

But the Sun's light only takes three minutes to travel to its closest planet, the little scorched world of Mercury.

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