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Well, Rory, thanks for writing. As I understand it, your info on constellations is pretty much correct.
The stars that we see in our skies are at all different distances from us … from just a few light years to hundreds, or at most a few thousand. The most distant object we Myths and ever likely to see with the naked eye is the Andromeda Galaxy, at about 2.5 million light years, which of course is well outside our own Milky Way Galaxy, which contains ALL the separate stars we see in the sky.
Since the stars are fairly randomly distributed along any line of sight, it’s pot luck as to what shapes, or constellations, they form as seen from Earth. The stars of the Plough, for instance, though forming a nice group in our skies, are at all different distances from us, and moving in different directions, so in a few million years the Plough will look very different.
However, as you say, some groups we see actually ARE close together in space. This is certainly true of the Pleiades, which are a genuine stellar cluster situated at about 440 light years from us. The core of this cluster is only 8 light years across. And most (though not all) of the stars in Orion are also close to each other in space. Looking at the list, the major stars in Orion are anything from 243 to 1,360 light years from us. So this is a real group, but not nearly so compact as the Pleiades.
I’m not alone in finding the shape of the Orion constellation inspiring; it was seen by almost every ancient civilisation as the representation of a strong man in the Heavens. A pure accident? Well, if so, a happy one at least. It has certainly given me strength at times of doubt.
Here’s a stereo picture to free-view, a schematic 3-D representation of Orion, giving an idea of the relative distances of its component stars. Note that the fuzzy patch around the centre star in Orion’s belt is NOT a galaxy, but a nebula – a cloud of gas and dust, out of which stars are being born – which itself is about 1,500 light years away from Australia !