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Globular clusters are what they sound - huge balls of stars. Again they'll have been born together, but globular clusters tend to be split apart by gravitational forces. We see them now around the very edges of the galaxy, tucked out of the way, and they tend to be very old stars. Our Sun would almost certainly have been born in a cluster - an open cluster - which has drifted apart.       

Our Sun and its solar system lie in a spiral arm of a galaxy rather like this one. Because of our position we can see a band of stars running acrss the sky that we call the Milky Way. If you look with a pair of binoculars you'll see just how thick with stars it is. This is the view towards the centre of our galaxy. Look in any other direction and although there are still plenty of stars, there are far fewer than there are in the Milky Way. That's because you're now looking out of the galaxy, and because there are fewer stars in the way, that's where you'll see star clusters and nebulae within our galaxy, and other galaxies which of course aren't. Many galaxies exihibit the same sort of structure as our own - with a central bulge at the core and arms of stars spiralling outwards. Some, however, don't, and this could be due to interactions with other galaxies. Space may be relatively empty, but structures as huge as galaxies do pass close to each other, and sometimes collide.

There is another structure which looks rather similar to galaxy but much smaller, and that's a solar system.. What we find in solar systems like our own - planets, asteroids, meteors and comets - are the left overs from star formation, but it should be obvious to any of you reading this that the Earth isn't made of hydrogen, or helium, like stars, so where did the other elements come from?

This is where they came from. A dead star. The reaction is stars doesn't stop when all the hydrogen is converted to helium. The helium itself then reacts and forms the heaver elements, including carbon, without which we wouldn't be here. Once all the reactions come to an end the star expands hugely, then collapses in on itself, throwing off an outer shell of material. The image you're looking at here is M1, the Crab Nebula, and it's known as a supernova remnant. It's the leftovers from a large, hot, fast burning star which was observed to go supernova in 1054. It's quite small as yet, and as such is quite easy to see with a small astronomical telescope, but if you can find a photograph of the Veil Nebula in Cygnus you'll get some idea of how the Crab might look in around fifty thousand years' time, because it's expanding - in fact very quickly - but because it's about six thousand light years away we don't see it.

Our own Sun, which is saner and rather more boring, will end its days something like this, as a planetary nebula, but will still have gone through the same helium to heavier elements process, and when that material is thrown out into space it can ultimately come together in another star and its solar system. So the elements for planets and life weren't there from the beginning - they've evolved through the life and death of stars before ours.

Our solar system, as far as we know, consists of a star and eight planets, of which half are rocky and comparatively close to the Sun, and half are gas giants and much further from the Sun. Then there are numerous moons and asteroids, one of which is thought of as a planet - hello Pluto - comets in orbit around the Sun and Jupiter, and meteors, which are comets' left overs. It is pure chance that our solar system has a rocky planet large enough to maintain an atmosphere, at the right distance from the Sun to start and sustain life, and a gas planet large enough to 'mop up' a lot of the debris that might otherwise hit other planets, which has allowed life to evolve for long enough to acquire intelligence.......allegedly. As to how life started here on Earth, and the question of life on other planets - well that's another story.

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